| No. | Term | Definition |
|---|---|---|
| 1. | Ace | Team’s top starting pitcher. |
| 2. | Advanced stats | Metrics beyond traditional batting and pitching. |
| 3. | AL | American League. |
| 4. | Arbitration | Salary-setting process for eligible players. |
| 5. | Around the horn | Infield double play: 5-4-3 or 6-4-3. |
| 6. | At-bat (AB) | Plate appearance excluding walks and sacrifices. |
| 7. | Balk | Illegal pitching motion with runners on. |
| 8. | Barrel | Ideal contact: high exit velocity, launch angle. |
| 9. | Bat flip | Showy toss after big hit. |
| 10. | Batting average (AVG) | Hits divided by at-bats. |
| 11. | Beat the shift | Hit where defenders aren’t positioned. |
| 12. | Bullpen | Relief pitchers and their area. |
| 13. | Bunt | Softly tapped ball to advance runners. |
| 14. | Called strike | Pitch in zone not swung at. |
| 15. | Catcher framing | Receiving to make pitches look strikes. |
| 16. | Changeup | Offspeed pitch mimicking a fastball. |
| 17. | Closer | Reliever who finishes games, often 9th. |
| 18. | Clubhouse | Team’s private locker and meeting area. |
| 19. | Cycle | Single, double, triple, homer in game. |
| 20. | Defensive indifference | No attempt to stop a steal. |
| 21. | Designated hitter (DH) | Bats instead of pitcher; doesn’t field. |
| 22. | DFA | Designated for assignment; removed from 40-man. |
| 23. | Double play | Two outs recorded on one play. |
| 24. | Dugout | Team bench area along foul lines. |
| 25. | Earned run (ER) | Run not due to error or passed ball. |
| 26. | ERA | Earned runs allowed per nine innings. |
| 27. | Exit velocity | Speed of ball off the bat. |
| 28. | Extra-base hit (XBH) | Double, triple, or home run. |
| 29. | Fair ball | Batted ball landing inside foul lines. |
| 30. | Fastball | Hardest pitch type; various grips. |
| 31. | Fielding percentage | (Putouts+assists) divided by chances. |
| 32. | Five-tool player | Hits, power, runs, throws, fields well. |
| 33. | Flyout | Out on caught ball in air. |
| 34. | Force out | Runner out because must advance. |
| 35. | Forkball | Split-fingered drop pitch variant. |
| 36. | Free agency | Players can sign with any team. |
| 37. | Full count | Three balls, two strikes. |
| 38. | Game 162 | Regular-season finale; often decisive. |
| 39. | Gold Glove | Award for top defensive player. |
| 40. | Grand slam | Home run with bases loaded. |
| 41. | Ground-rule double | Fair ball bounces into stands. |
| 42. | Groundout | Out on ground ball. |
| 43. | Hall of Fame | Cooperstown honors baseball’s greatest. |
| 44. | Hard-hit rate | Percent of balls hit 95+ mph. |
| 45. | Hold (HLD) | Reliever preserves lead before save. |
| 46. | Home run (HR) | Hit allowing batter to score instantly. |
| 47. | Infield fly rule | Automatic out on easy pop with force. |
| 48. | Innings pitched (IP) | Outs recorded by pitcher, expressed in innings. |
| 49. | Intentional walk (IBB) | Deliberate four balls to avoid hitter. |
| 50. | Jack | Slang for home run. |
| 51. | Knuckleball | Fluttering pitch with minimal spin. |
| 52. | Launch angle | Vertical angle of batted ball. |
| 53. | Leadoff hitter | First batter in lineup; sets table. |
| 54. | Line drive | Hard, low trajectory batted ball. |
| 55. | Lineup card | Official batting order and positions. |
| 56. | LOB | Left on base; runners stranded. |
| 57. | Magic number | Wins needed to clinch over rival. |
| 58. | Manager | On-field leader making tactical decisions. |
| 59. | Middle relief | Relievers used before late innings. |
| 60. | Minor leagues | Development system below MLB. |
| 61. | Moneyball | Roster-building via analytics and value. |
| 62. | Mound visit | Conference at pitcher’s mound. |
| 63. | National anthem | Pre-game ceremonial song. |
| 64. | NL | National League. |
| 65. | No-hitter | No hits allowed in complete game. |
| 66. | On-base percentage (OBP) | Times on base per plate appearance. |
| 67. | Opener | Reliever starts to face top hitters. |
| 68. | OPS | OBP plus slugging percentage. |
| 69. | Outfield assist | Out made by outfielder’s throw. |
| 70. | Pennant | League championship; World Series berth. |
| 71. | Pickoff | Pitcher throws to base to catch runner. |
| 72. | Pinch hitter | Substitute batter for a plate appearance. |
| 73. | Pinch runner | Substitute baserunner, often for speed. |
| 74. | Pitch clock | Timer limiting pitch and between-batter time. |
| 75. | Pitch count | Number of pitches thrown by pitcher. |
| 76. | Pitcher’s duel | Low-scoring game dominated by pitchers. |
| 77. | Platoon | Split playing time by handedness matchups. |
| 78. | Postseason | Playoffs after regular season. |
| 79. | Qualifying offer | One-year contract offer to free agent. |
| 80. | Quick pitch | Pitch before hitter is set; often illegal. |
| 81. | RBI | Run batted in; credit for scoring runner. |
| 82. | RISP | Runners in scoring position: 2nd or 3rd. |
| 83. | Rookie | First-year player under MLB limits. |
| 84. | Run differential | Runs scored minus runs allowed. |
| 85. | Rundown | Tag play between bases; “pickle”. |
| 86. | Sacrifice fly | Flyout scoring runner from third. |
| 87. | Save (SV) | Relief preserves lead under save rules. |
| 88. | Scorekeeper | Official records game’s plays and stats. |
| 89. | Seam-shifted wake | Pitch movement from seam airflow effects. |
| 90. | Shift | Defensive repositioning based on tendencies. |
| 91. | Slider | Breaking pitch with lateral movement. |
| 92. | Slugging percentage (SLG) | Total bases divided by at-bats. |
| 93. | Spin rate | Revolutions per minute of a pitch. |
| 94. | Split-finger fastball | Fastball variant with sharp drop. |
| 95. | Spray chart | Map showing where balls are hit. |
| 96. | Starter | Pitcher who begins the game. |
| 97. | Steal | Advancing base during pitch to plate. |
| 98. | Strike zone | Area over plate where pitch is strike. |
| 99. | Strikeout (K) | Batter out on three strikes. |
| 100. | Suspension | Disciplinary ban for set games. |