relief pitcher

noun, Baseball.
1.
a pitcher brought into a game to replace another pitcher, often in a critical situation.
2.
a pitcher regularly so used, as opposed to one who regularly starts games.
Also called reliever, reliefer.
Origin
1945-50
British Dictionary definitions for relief pitcher

relief pitcher

noun
1.
(baseball) a pitcher who replaces a side's main pitcher during a game Also called reliever