WordNet records no synonym and no antonym for barbary coast. It is the only member of each of its synsets, 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 part of a city that is notorious for gambling dens and brothels and saloons and riotous night life (especially the waterfront of San Francisco after the gold rush of 1849)
“we'll tolerate no Barbary Coast in this city!”
the Mediterranean coast of northern Africa that was famous for its Moorish pirates
Synonyms, antonyms and the broader and narrower relations for barbary coast come from Princeton University’s WordNet. Full sources and licences.