In baseball, what is the infield fly rule?

Answer 1

From Rule 2.0 of the MLB rules:

An INFIELD FLY is a fair fly ball (not including a line drive nor an attempted bunt) which can be caught by an infielder with ordinary effort, when first and second, or first, second and third bases are occupied, before two are out. The pitcher, catcher and any outfielder who stations himself in the infield on the play shall be considered infielders for the purpose of this rule.
When it seems apparent that a batted ball will be an Infield Fly, the umpire shall immediately declare “Infield Fly” for the benefit of the runners. If the ball is near the baselines, the umpire shall declare “Infield Fly, if Fair.”
The ball is alive and runners may advance at the risk of the ball being caught, or retouch and advance after the ball is touched, the same as on any fly ball. If the hit becomes a foul ball, it is treated the same as any foul.
If a declared Infield Fly is allowed to fall untouched to the ground, and bounces foul before passing first or third base, it is a foul ball. If a declared Infield Fly falls untouched to the ground outside the baseline, and bounces fair before passing first or third base, it is an Infield Fly.

Answer 2

Rule 2.0 is not a correct reference.

Rule 6.05e: The Infield Fly Rule is a rule in baseball that prevents unfair gamesmanship by the fielders. The infield fly rule applies when there are fewer than 2 outs, and there are runners on first and second base, or on first, second and third base. In these situations, if a fair fly ball is hit that, in the umpire's judgment, is catchable by an infielder with ordinary effort, the batter is out regardless of whether the ball is actually caught in flight. The rule states that the umpire is supposed to announce, "Infield fly, if fair". If the ball will be almost certainly fair, the umpire will likely yell, "Infield fly, batter's out!" or just "Batter's out!"

On a caught infield fly, the runners must tag up and may attempt to advance, like on any catch. If the infield fly is not caught, runners need not tag up. In either case, since the batter is out, the force play on other runners is removed.

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...so basically if the ump calls the infield fly rule you need to play it like an outfield pop-up (ie, tag-up or get back to the base) otherwise the infielders can intentionally drop the ball and pull a double play.

Answer 3

The Infield Fly Rule applies when there are less than two outs and runners on first and second. If the ball is popped up in the infield, the batter is automatically called out, regardless of whether or not the fielder catches the ball. This rule exists to prevent a fielder from intentionally dropping an easy pop fly to get a cheap double or triple play.

Answer 4

WIth runners on 1st and 2nd or bases loaded and less than two outs, if the batter hits a fly ball that can be fielded with ORDINARY EFFORT by one of the infielders, then the batter is automatically out (even if the ball is dropped). Runners may advance at their own risk.

The purpose of this rule is to keep the defense from getting an easy double play by intentionally dropping a fly ball.

Answer 5

http://en.wikipedia.org/wiki/Infield_fly_rule