A foul ball is a ball that has been hit and lands in foul territory between home and first base, or between home and third base. A foul ball is also any ball that bounds past first or third base on or over foul territory, or that falls on foul territory beyond first or third base before it is touched, such as a fly ball. Also, this never happens but it could in theory. 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.