1. a line from which basketball players take penalty shots;
2. a line across a bowling alley that a bowler must not cross;
3. lines through 1st and 3rd base indicating the boundaries of a baseball field;
WordNet (r) 3.0 (2006):
foul line
n 1: a line from which basketball players take penalty shots
2: a line across a bowling alley that a bowler must not cross
3: lines through 1st and 3rd base indicating the boundaries of a
baseball field