It's a baseball term, long is use here in the US. It's a good thing.

Too bad my local team lost the World Series (As Peter Sagal noted on Wait! Wait! Don't Tell Me! last week, "An American team is once again expected to win the World Series.")

Pinch hitter from Wikipedia:

In baseball, a pinch hitter is a substitute batter. Batters can be substituted at any time while the ball is dead (not in active play); the manager may use any player that has not yet entered the game as a substitute. Unlike basketball, American football, or ice hockey, however, baseball does not have a "free substitution rule" and thus the replaced player in baseball is never allowed back into that game. The pinch hitter assumes the spot in the batting order of the player he replaces.

Pinch hitters are often used to replace a starting player when the pinch hitter is thought to have a better chance of reaching base or helping other runners to score.

In the National League of Major League Baseball, the Central League in Japan, and various other minor leagues, pinch hitters are often substituted for the pitcher in the middle or late innings of a game. This is because pitchers are often poor hitters and get tired after six to seven innings of pitching. This use of a pinch hitter is often part of a double switch, in which a relief pitcher replaces a defensive player who will not bat soon, and a defensive player replaces the former starting pitcher that is currently up to bat. This strengthens the lineup in the short term by preventing the relief pitcher from batting and allowing a better hitter to bat. Compared to a single substitution of a pinch hitter for a pitcher, this allows the relief pitcher to pitch additional innings. A pinch hitter can be substituted at any time in an at-bat.

The pinch hitter may remain in the game following a pinch-hit at-bat and need not (but may) assume the same position as the player for whom he pinch-hits as long as some other player assumes that position. For example, on 16 August 2009, the Washington Nationals' Ryan Zimmerman pinch-hit for second baseman Alberto Gonzalez and then remained in the game at third base, with previous third baseman Ronnie Belliard switching positions to play second base after the change. (Box score: [1]) Alternatively, the manager may designate another player to replace the pinch-hitter; this scenario is common when a team pinch-hits for a pitcher without executing a double switch, such that the new pitcher then replaces the pinch hitter and assumes the previous pitcher's place in the batting order.

The American League of Major League Baseball, the Pacific League in Japan, and various other leagues use the designated hitter rule, such that pitchers seldom bat. This removes one possible situation where a pinch hitter may be desired.

It's a great game, much easier to understand and faster than cricket. :)

SRS