foul line is a noun meaning "a line from which basketball players take penalty shots". It carries 3 recorded senses.
a line across a bowling alley that a bowler must not cross
lines through 1st and 3rd base indicating the boundaries of a baseball field
Definitions, synonyms and semantic relations for foul line come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.