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Baseball Terms Glossary
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This is an alphabetical list of selected unofficial and specialized terms, phrases, and other jargon used in baseball, and their definitions, including illustrative examples for many entries.

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When a fielder illegally hinders a baserunner, the fielder is guilty of obstruction. The only time a fielder need not "get out of the way" of a baserunner is when the fielder is fielding or in possession of the ball.


See on base percentage.


A batter who goes hitless in a game, as in "0 for 4" (spoken as "oh for four"). Also wears the collar.

official game

A game that can be considered complete. If more than half the game has been played before being called by an umpire, it is considered "official" and all records from the game are computed in the players' and teams' statistics. For a 9-inning game, five innings need to be played, or four-and-a-half if the home team is in the lead. A game that cannot be considered complete can either be suspended or replayed from the first inning.

official scorer

The official scorer is a person appointed by the league to record the events on the field and to send this official record to the league offices. The official scorer never goes on the field during a game (but typically watches from the press box). The official scorer's judgments do not affect the progress or outcome of the game but they do affect game and player statistics. For example, only umpires call balls and strikes, whether a batted ball is fair or foul, whether a hit is a home run, and whether runners are safe or out. But it's the official scorer who determines whether a pitch that gets by the catcher is a wild pitch or a passed ball or whether a batted ball is a hit or an error (or a combination of the two), and who gets credited with an error, put-out, or assist.


  • A day when a player performs below his normal level, whether due to illness, bad luck, or other factors. "Bonderman had an off-day and didn't have good command of his breaking pitches."
  • A day when a team does not have a game scheduled. During the regular season, Major League Baseball teams almost always have games scheduled on Fridays, Saturdays, and Sundays, and they may need to travel between series. Off-days tend to occur on Mondays and Thursdays.

off-speed pitch

A pitch that is significantly slower than a given pitcher's fastball. Typically, a curveball or a change-up.


Overall Future Potential (OFP) is a scouting assessment of a young player's potential as a future major leaguer, scored from 20 to 80. The criteria are different for pitchers and position players. See also tools.

Ol’ Number One

The fastball. From the sign the catcher gives for that pitch.

Olympic Rings

When a batter strikes out five times in a game. This same dubious achievement may also merit a Platinum Sombrero.

on a line

When an outfielder throws the ball directly to an infielder or the catcher without relaying it or bouncing it, he's said to "throw the ball on a line." Usually used when a strong throw beats the runner and gets him out. "Jack Barry, however, made a running stab to grab the ball and threw on a line to McInnis for an out."

On base percentage (OBP)

Percentage of at-bats where a batter reaches base for any reason other than an error or a fielder's choice or being hit by a pitch.


The next batter due to bat after the current batter. The area designated for the on-deck batter is a circle 5 feet (1.5 m) in diameter, officially called the "next batter's box" and commonly called the "on-deck circle." Ironically, the on-deck batter rarely stands in the on-deck circle.

on the black

  • The edge of home plate, derived from the black border of the plate that is buried when the plate is correctly installed.
  • A pitch that just nicks the edge of the zone for a called strike.

on the board

A team is "on the board" (i.e., the scoreboard) when it has scored one or more runs. "After being shut out for 6 innings, the Sox are finally on the board." White Sox announcer Hawk Harrelson also uses the phrase as part of his home run call: "You can put it on the booooard... YES!"

on the farm

When a player is playing in the minor leagues, he is said to be spending time "on the farm." It refers to a team's farm system.

on the interstate

A player batting between .100 and .199 is said to be "on the interstate." The term refers to the fact that a batting average in the .100s can resemble an interstate name (e.g. .195 resembles I-95), especially on older scoreboards where the numeral "1" appears identical to the uppercase letter "I" (with no serifs). A hit to put an average above .200 gets a batter "off the interstate." A batter whose average is below .100 is sometimes said to be "off the map". See also Mendoza line. Players in the majors who spend too much time "on the interstate" will most likely be demoted to AAA for seasoning.

on the rug

A player is said to be "on the rug" while playing a ball in the outfield on artificial turf.

on the throw

  • A defensive attempt to put out a baserunner attempting to reach more bases than the type of hit would typically allow, such as a runner on first attempting to advance to third on a single.
  • Also refers to the successful advance of a baserunner while such a play is being attempted on his teammate. See also: fielder's choice.
  • A batter who safely reaches first base but is tagged out attempting to reach a subsequent base on the same play is credited with a hit for the number of bases he safely reached, but is said to be out on the throw.
  • Example: With Abel on first base, Baker hits a base hit to center field. Abel easily reaches second and tries to advance to third, but the throw from the outfield is in time and he is tagged out by the third baseman. Meanwhile, Baker has safely reached second base. Abel is out at third base on the throw. Baker has a single and advanced to second on the throw. The next batter, Charlie, hits a double to the center field wall, allowing Baker to score from second. Charlie safely rounds first and second base and attempts for third, but the throw from center field is in time and Charlie is tagged out at third base. Charlie is credited with an RBI double, but is out at third base on the throw.

one-game wonder

A player who appears in just one major league game, plays respectably, and then is either demoted to the bench or the minor leagues.


A game in which one team was limited to one hit, a great feat for a pitcher. Batters may have reached base via walks, errors, or being hit by a pitch. See also no-hitter and perfect game.

one-two-three inning

Side retired in order. Three up, three down.

opposite field hit

A hit to the "opposite" side of the field from the direction of a player's natural swing, i.e., a left-handed batter who hits to left field or a right-handed batter who hits to right field. Also known as going the other way. See pull hitter.

OPS (On-base Plus Slugging)

A term recently invented by statheads to measure of a batter's ability to produce runs. Obtained by adding slugging average and on-base percentage.

ordinary effort

Defined in MLB Rule 2 as "the effort that a fielder of average skill at a position in that league or classification of leagues should exhibit on a play, with due consideration given to the condition of the field and weather conditions." A defensive player's ordinary effort is considered by the official scorer in making certain judgment calls, such as errors, wild pitches, the infield fly rule, etc.

out pitch

The type of pitch that a pitcher relies on to get a batter out. This is often the pitcher's best pitch. Headline: "Angels Notebook: Rodriguez embraces change as out pitch".


An outfielder is a player whose position is either left field, center field, or right field. See position.

outside corner

The location of a strike that travels over the far edge of home plate from the batter.

overpower the hitter

To throw a pitch that is so fast the batter cannot catch up to it with his swing. "And eight runs were more than enough offense to back Wolfe, as he continually overpowered hitters with his blazing fastball. Santa Clara hitters just couldn't catch up to it.


  • When a fielder throws the ball so high that it sails over the head and out of reach of an infielder. "Sean Halton struck out, but the catcher couldn’t hold onto the pitch, and then overthrew first base, which allowed both Martin and Greene to score".
  • If a thrown ball goes over the head or wide of the infielder and sails off the field of play into the dugout or the stands, the umpire will rule an overthrow and allow the runner to advance one base.
  • A pitcher who throws the ball too hard to control it well is said to be "overthrowing the ball". "Gardenhire said Crain, demoted to Class AAA Rochester earlier this season, is pitching with more confidence and, most importantly, he's not trying to overthrow the ball".

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Published - February 2011

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