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Baseball Glossary
Learn the language of Baseball — answer-first definitions with real examples, beginner to pro.
273 terms
- Age vs Level (Scouting)IntermediateAge vs level weighs a player's stats against how old they are for their level. Being young for a level is generally good; being old tempers strong numbers.
- Ahead vs Behind in the CountBeginnerMore balls than strikes is a hitter's count; more strikes than balls is a pitcher's count. Which side holds the edge reshapes how both of them play the rest of the at-bat.
- Arm AngleIntermediateArm angle is the vertical orientation of the throwing arm at release — from over-the-top through three-quarter, sidearm, to submarine — and it shapes both the pitch plane and movement profile.
- Arm Care RoutineBeginnerAn arm care routine is a regular set of general warmup, mobility, and strengthening exercises for throwers. It is usually done before and after throwing.
- Arm Slot (Fielding)IntermediateA fielder's arm slot is the arm angle at release when throwing. The natural slot produces the most accurate and arm-safe throw for that player's anatomy.
- Attack Angle (Batting)AdvancedAttack angle in batting is the vertical angle of the bat path through the hitting zone. A slightly upward attack angle matches the pitch plane for hard contact. Statcast treats 5 to 20 degrees at contact as the ideal range.
- Attack DirectionAdvancedAttack direction is the left-to-right direction the bat's sweet spot is moving at contact, measured in degrees toward the pull side or the opposite field from a line to straightaway center. The MLB average is about 2° pull, and most hitters' season averages fall between about 15° pull and 10° opposite field. It mostly reflects timing: an early swing points the bat toward the pull side, and a late one toward the opposite field.
- BABIP (Batting Average on Balls in Play)IntermediateBABIP is batting average on balls in play: hits that are not home runs, divided by the balls a hitter puts in play. The formula is (H − HR) ÷ (AB − K − HR + SF). League average is almost always around .300. Line drives fall for hits more often than ground balls, and ground balls more often than fly balls. As a result, hard line-drive contact helps. But short streaks are mostly luck.
- Backdoor Breaking BallAdvancedA backdoor breaking ball starts off the plate and breaks back over the outside corner for a called strike. It looks like a ball until the last instant.
- Backhand FieldIntermediateFielding a ground ball backhand means turning the back of the glove hand toward the ball. The fielder reaches across the body instead of squaring up.
- Backspin (Batting)IntermediateBackspin is backward rotation on a batted ball from contact slightly below center. Its Magnus effect helps fly balls and line drives carry instead of diving.
- BalkIntermediateA balk is an illegal or deceptive motion by the pitcher with runners on base. Every runner is immediately awarded one base, and no pitch needs to be thrown.
- Ball TransferIntermediateBall transfer is the exchange of the ball from glove to throwing hand. Its speed and consistency are among the biggest separators for infielders and catchers.
- BarrelAdvancedA barrel is a batted ball with both high exit velocity and an optimal launch angle. That combination is the one most likely to produce extra-base hits.
- Barrel AccuracyAdvancedBarrel accuracy is how reliably a hitter finds the bat's sweet spot rather than the handle or end cap. It differs from the formal "barrel" stat.
- Barrel Diameter (Big Barrel Bats)Beginner"Big barrel" describes a bat with a barrel 2⅝ or 2¾ inches across. USSSA's bat rules group those as big barrel bats, apart from small barrel bats of 2¼ inches or less. Little League caps non-wood bats at 2⅝ inches in its main divisions. MLB wood bats can be no more than 2.61 inches thick.
- Barrel PathIntermediateBarrel path is the route the barrel takes through the hitting zone. Matching it to the pitch plane as long as possible gives the best odds of hard contact.
- Baseball IQIntermediateBaseball IQ is a player's game awareness and decision-making, apart from physical tools. It is knowing where to throw, when to run, and how to position.
- Baserunning ReadIntermediateA baserunning read is the split-second decision a runner makes based on what the ball does after contact — whether to advance, hold, or retreat.
- Bat DragIntermediateBat drag is a sequencing fault where the hands race ahead and the barrel trails behind. It costs bat speed and forces contact deep, off the sweet spot.
- Bat DropBeginnerA bat's drop is its length in inches minus its weight in ounces. A 30-inch bat that weighs 20 ounces is a drop 10, written -10, and the bigger the number. The lighter the bat is for its length. Easton's guide says players under 11 usually use a -10 or lighter and older players can often move to a -8 or -5. High school and college non-wood bats meet the BBCOR standard, which means a -3.
- Bat PathBeginnerBat path is the 3D route the barrel travels from load to finish. Its shape through the zone, more than raw bat speed, decides hard or weak contact.
- Bat Sensor AccuracyIntermediateBat sensors are fairly accurate for bat speed but less so for swing angles. A 2022 study compared four commercial sensors with a motion-capture system. Swing speed agreed well, swing angles agreed less, and every sensor had some built-in bias. Use one sensor to track your own trends rather than to compare brands or players.
- Bat Size by AgeBeginnerEaston's age chart, a common starting point, suggests 24–26 inch bats for ages 5–7, 26–28 for 8–9, 28–29 for age 10 and 30–31 for 11–12. For older players it suggests 31–32 inches at 13–14, 32–33 at 15–16 and 34 at 17 and up. Then fine-tune by fit: pick a bat the player can swing fast and control, with the certification stamp your league requires.
- Bat SpeedIntermediateBat speed is how fast the barrel is moving at contact, in mph. It contributes to exit velocity alongside bat path and where on the barrel you make contact.
- Bat Speed by AgeIntermediateBlast Motion, a bat-sensor maker, publishes practice-swing ranges of about 30–45 mph for 8- to 10-year-olds and 40–52 for 11- to 12-year-olds. For older players its ranges are about 46–62 mph at 13–14, 55–65 at 15–16 and 60–70 at 17–18. Treat them as rough guides from one sensor in tee and toss work. In MLB, Statcast's average swing was about 72 mph when bat tracking launched in 2024.
- Bat StingBeginnerBat sting is the painful buzz you feel when the ball meets the bat away from its sweet spot. The impact makes the bat vibrate, and the vibration runs down the handle into your hands. Contact off the end of the barrel tends to buzz the bottom hand, while contact toward the thin part of the bat stings the top hand between the thumb and index finger. Squarer contact is the real fix; batting gloves and bats built to damp vibration soften it.
- Bat-to-Ball SkillBeginnerBat-to-ball skill is the ability to make solid contact reliably. It covers tracking, timing, and getting the barrel to the ball, not how hard the ball is hit.
- Batted Ball Event (BBE)IntermediateA batted ball event is any batted ball that produces a result: a hit, an out or an error. Every fair ball counts, and so does a foul ball caught for an out. Other foul balls do not count. Statcast uses batted ball events to figure average exit velocity, launch angle, hard-hit rate and barrel rate.
- Batter's Box RuleBeginnerA batter who hits the ball, fair or foul, with a foot on the ground entirely outside the batter's box is out. That is MLB Rule 6.03(a)(1) and NFHS Rule 7-3-2. The chalk lines belong to the box. A foot touching a line is legal. High school rules also call a batter out for making contact with a foot on home plate.
- Batting AverageBeginnerBatting average is hits divided by official at-bats. Walks, hit-by-pitches, sacrifices and catcher's interference do not count as at-bats. A .300 average has long been seen as a strong mark in pro baseball. What counts as good in youth or high school ball depends a lot on the league and the pitching.
- Batting Grip (How to Hold a Bat)BeginnerHold the bat in your fingers, not deep in your palms, with your hands touching and the bottom hand just above the knob. Many coaches line up the door-knocking knuckles of both hands, or set them a little toward the big knuckles. Keep the grip firm but relaxed so the wrists and forearms stay quick.
- Batting Helmet (NOCSAE, C-Flap)BeginnerA batting helmet must meet the NOCSAE standard for batter's headgear and carry the NOCSAE stamp. High school rules require one with ear flaps on both sides for batters, on-deck batters and runners. A C-flap or face guard adds jaw and face protection. NFHS rules allow one but do not require it. A good fit is snug with no wobble.
- Batting Order Roles (Leadoff, Cleanup)BeginnerA good leadoff hitter gets on base often, sees a lot of pitches and can run. The top of the order is usually the best on-base hitters. The middle, including the cleanup spot in fourth, holds the best power hitters. The bottom has the weaker bats. Some coaches bat their best hitter second because top spots come up most often.
- Batting Out of OrderIntermediateIf you bat out of order, nothing happens unless the other team appeals. If they appeal while the wrong batter is still up, the right batter steps in and takes over the count. If they appeal after the wrong batter finishes but before the next pitch. The proper batter is out and any advance from the hit is cancelled. Once the next pitch is thrown, the wrong at-bat stands.
- Batting Practice StructureIntermediateGood batting practice gives every round a goal. Many coaches move from tee and toss to machine or live pitching, and from set locations to mixed ones. Rounds focus on one job, such as opposite-field line drives, bunts or a two-strike approach. Competitive rounds that score hard contact add game pressure.
- Batting StanceBeginnerA good batting stance is balanced and relaxed. Set your feet a little wider than your shoulders, bend your knees slightly and keep your weight on the balls of your feet. Hold your hands near the back shoulder with both eyes level on the pitcher. Square, open and closed setups all work if you land balanced and on time.
- Batting Tee Work (Tee Placement)BeginnerTee work is hitting a ball off a stationary batting tee to groove the swing. Place the tee where you want contact. For a middle pitch, that is usually a little in front of the front hip. Move it deeper for an outside pitch and farther out front for an inside pitch, and set the height to the part of the zone you are working on.
- BBCOR BatBeginnerBBCOR (Batted Ball Coefficient of Restitution) is the performance standard that high school and college baseball require for non-wood bats. A legal bat carries a permanent 'BBCOR .50' mark and performs close to wood. Under NFHS high school rules it can weigh no more than 3 ounces less than its length (a drop -3). Its barrel can be no wider than 2 5/8 inches.
- Blast (Bat Tracking)AdvancedA blast is a Statcast bat-tracking term for a swing that is both fast and squared up. A swing counts as a blast when its squared-up percentage times 100, plus its bat speed in mph, is at least 164. It rewards hitters who combine bat speed with solid contact.
- Blocking a Pitch (Catching)IntermediateBlocking is when a catcher smothers a pitch in the dirt with the body and chest protector, not the glove. It keeps the ball in front, preventing a passed ball.
- Bullpen SessionBeginnerA bullpen session is a pitcher's practice throwing, usually off a mound, working the pitch mix at game-like intent. There are no live hitters or game pressure.
- Bunt TechniqueBeginnerBunt technique is deadening the ball by absorbing its speed instead of swinging. It uses soft hands, a squared or angled stance, and the bat as a cushion.
- Called Strike RateAdvancedCalled strike rate is the share of in-zone pitches a hitter takes for a strike. It mirrors chase rate, measuring missed chances instead of bad swings.
- Called-Strike-Plus-Whiff Rate (CSW%)AdvancedCSW% is called strikes plus swinging strikes (whiffs) as a share of all pitches thrown. It shows how often a pitcher gets a strike without a ball in play.
- Carry (Throw)IntermediateCarry is how well a throw holds its speed and straight line without tailing, sinking, or losing steam. A throw that "carries" arrives true to the target.
- Casting (Batting)IntermediateCasting is a swing fault where the hands and barrel arc wide instead of taking a direct path to the ball. It kills bat speed and limits inside coverage.
- Catcher's InterferenceIntermediateCatcher's interference is when the catcher, or any fielder, interferes with the batter during a pitch, usually by touching the bat with the mitt as the batter swings. Under MLB Rule 6.01(c), the batter is awarded first base. If a play follows, the offense's manager can choose to take the result of the play instead.
- Catcher's Setup TargetBeginnerA catcher's setup target is the glove spot shown before the pitch. It gives the pitcher a clear, steady point to aim at and signals the intended location.
- Ceiling vs Floor (Scouting)IntermediateCeiling is a player's realistic best-case outcome; floor is the realistic worst case if development stalls. Scouts weigh both, not just the exciting one.
- Changeup (Pitching)IntermediateThe changeup is an off-speed pitch thrown with fastball arm speed but held deeper in the hand to reduce velocity by 8–15 mph, disrupting timing.
- Charging a Ground BallBeginnerCharging a ground ball means running at a slowly hit ball instead of waiting. It shortens the throw and keeps a bunt or slow roller from becoming a hit.
- Chase ContactAdvancedChase contact rate is the percentage of swings at pitches outside the strike zone that make contact. It shows how well a hitter survives a swing at a bad pitch.
- Chase RateIntermediateChase rate is the percentage of pitches thrown outside the strike zone that a hitter swings at. A core plate-discipline metric where lower is almost always better.
- Check SwingIntermediateA check swing is a swing the hitter stops before the bat crosses the plane of contact. It counts as a swing if the bat and wrists broke toward the ball.
- Chicken Wing (Hitting)IntermediateIn hitting, a chicken wing is when the front elbow lifts and bends out at contact instead of extending through the ball. It is usually a problem. It often comes from pulling off the ball or a rushed turn, and the barrel cuts across and leaves the zone early. A bent front arm on an inside pitch is normal, though.
- Circle Changeup GripIntermediateThe circle changeup grip forms a circle with the thumb and index finger on the side of the ball. It is built to cut velocity without changing arm speed.
- Coach-Pitch and Machine-Pitch HittingBeginnerIn coach pitch, an adult throws easy pitches from a short distance so young hitters can learn timing. In machine pitch, a machine throws at a steady speed. To help a child, practice with gentle tosses from the same distance. Teach them to start the swing as the ball is released and to swing at good pitches only.
- Coachability (Intangibles)BeginnerCoachability is taking feedback without defensiveness and adjusting based on it. Scouts and coaches weigh this "intangible" alongside physical tools.
- Collapsing Back SideAdvancedCollapsing the back side is when the back knee and hip buckle and drop instead of staying stacked. It robs ground force and leaves the arms to do the work.
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