WordNet records no synonym and no antonym for free throw lane. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a lane on a basketball court extending from the end line to 15 feet in front of the backboard; players may not enter this lane during a free throw
Synonyms, antonyms and the broader and narrower relations for free throw lane come from Princeton University’s WordNet. Full sources and licences.