A pitch which is doctored by the pitcher to make it have a bending motion as it comes to the plate.The pitch is thrown with a different grip than the fastball in that a pitcher wedges the ball in between his fingers and delivers the pitch as if he were slamming his fist down on a table. This creates topspin on the ball which makes air moving around it curve to the axis rotation of the pitch.
"The only reason why the batter is the underdog in this game." ~Warren Spahn, Winningest lefty of all time
"Barry Zito's curveball is unhittable!"
"That curve he snapped off was perfect! Nose to knees..."
Usually a Baseball team's best relief pitcher. He comes in for the last inning to "shut the door" on the other team and preserve a tight game when his team is on top. As opposed to breaking balls and offspeed junk, he usually comes in and throws his outstanding fastball and, typically, slider.
The 8th inning is the real last chance for our sox to fight back. Mariano Rivera (most acclaimed closer ever) is warming up in the bullpen.