A FOUL BALL is a batted ball that settles on foul territory between home and first base, or between home and third base, or that bounds past first or third base on or over foul territory, or that first falls on foul territory beyond first or third base, or that, while on or over foul territory, touches the person of an umpire or player, or any object foreign to the natural ground.
A foul fly shall be judged according to the relative position of the ball and the foul line, including the foul pole, and not as to whether the infielder is on foul or fair territory at the time he touches the ball.
Rule 2.00 (Foul Ball) Comment: A batted ball not touched by a fielder, which hits the pitcher’s rubber and rebounds into foul territory, between home and first, or between home and third base is a foul ball.
If a ball settles completely on or over foul territory between home and first or third, it is a foul ball.
Fly ball falls foul between home and third and settles for a foul ball.
A ball bounding on or over foul territory when passing first or third base bag is a foul ball.
Bouncing ball gloved in foul territory close to third base.
A ball that is airborne and falls in foul territory beyond first, second or third is a foul ballBall hit just foul.
A ball that is airborne and enters dead ball territory over foul territory is a foul ball.Foul ball into the stands.
A ball that is touched while over foul territory by an umpire is a foul ball.
Umpire hit by a foul ball.
A ball that is touched while over foul territory by a fielder and is not caught is a foul ball.
Ball is touched while rolling foul between home and third base.
A ball is touched by a batter in his batter’s box is a foul ball.
Ball hits batter in box, foul ball (if batter is in “legal position,” then foul. One foot out, batter is out) Rule 6.05(g); [BRD 102]
Batter fouls ball off his helmet while in the batter's box
Bunted ball hits batter while in batter's box
"Natural" and "unnatural" objects are not strictly defined by the rules other than "object foreign to the natural ground." See also Rule 6.05. A batted ball that strikes an unnatural object over fair territory remains live. [J/R] Unnatural objects include a base, the pitcher's plate, the rosin bag, helmet, a broken bat, a sprinkler head, a bat ring, a pine tar rag, and the scoreboard. [J/R]
An unbroken bat is an unnatural object if the ball rolls up against it and there is no interference. [J/R]
Ball hitting power lines, tree limbs and other overhead objects is considered part of the "sky" and is generally considered a live ball [BRD 105] A ground rule could play a part here.
Fair ball hits an overhead speaker. Live ball.
Birds, animals, rocks, and dirt clods are all considered natural objects. Batted and thrown balls that strike natural objects remain live. [J/R]
Batted ball hits bird
A pitched ball that hits an animal over fair territory is immediately dead (no pitch)
Pitch hits bird
Squirrel runs in front of plate during pitch, but is not hit.
In a 1992 game between the Pittsburgh Pirates and the Chicago Cubs, the Pirates' Jay Bell executed a hit and run play with Kirk Gibson on first. The ball was hit to right and struck Kirk Gibson's helmet which was on the ground. The ball ricocheted to Cubs' second baseman Ryne Sandberg, who was able to retire Gibson in a rundown between second and third.
The ball struck an unnatural object (the helmet) over fair territory, so play continued.