1. Lines through 1st and 3rd base indicating the boundaries of a baseball field
   "The batter's hit landed just inside the foul line"
    
2. A line across a bowling alley that a bowler must not cross
   "He was penalized for stepping over the foul line"
    
3. A line from which basketball players take penalty shots
   "She stepped up to the foul line to take her free throws"

Derived forms: foul lines

Type of: line

Part of: alley, ball field, baseball field, bowling alley, diamond, key, paint, skittle alley [Brit]

Encyclopedia: Foul line