For "Slider," the mascot, see Slider (mascot)
In baseball, a slider (also known as a "nickel curve") is a pitch halfway between a curveball and a fastball, with less break but more speed than the curve. It will tend to drop less and move toward or away from the batter more than a curve. The extra speed can fool the hitter into thinking it is a fastball, until too late. Some pitchers also use a cut fastball (or cutter) which is one step closer than the slider to the fastball on the spectrum between fastballs and curves. A pitch that has movement similar to both a slider and a curveball is sometimes called a slurve.
From the batter's perspective, one of the telltale signs of a slider is the presence of a red "dot" on the ball as it rotates -- caused by the appearance of the ball's seams as it spins tightly through the air. Of course, even when the batter is armed with this knowledge, the slider remains one of the more difficult breaking balls to hit in all of baseball.
The slider is also sometimes called "the great equalizer", as its development caused pitchers to regain some dominance over hitters. The slider also causes great stress and wear on a pitcher's arm: for this reason the Dodgers organization forbade its pitchers to throw sliders for many years after the pitch became popular.
Pitchers known for throwing sliders include: