In baseball, an off-speed pitch similar to the curveball, that breaks towards the plate laterally and down. The slider is slower than a fastball but faster than a curveball.
A slider is gripped much like a two-seam fastball, except the index and middle fingers are off center, resting closer to an on the outward seam of the baseball. The pitcher's wrist is slightly cocked, but not twisted. The pitch is released from the thumb side of the index finger and the wrist is snapped to give the ball lateral spin. The slider has a noticeably smaller break than the curveball and generally favors movement over break.
Like many specialty or off-speed pitches, sliders are usually featured mainly by pitchers in relief. Many closers in baseball use sliders in addition to blistering fastballs to mix up the speed of their pitches and keep batters off guard.