WordNet records no synonym and no antonym for bevy. 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 large gathering of people of a particular type
“he was surrounded by a bevy of beauties in bathing attire”
a flock of birds (especially when gathered close together on the ground)
“we were visited at breakfast by a bevy of excited ducks”
Synonyms, antonyms and the broader and narrower relations for bevy come from Princeton University’s WordNet. Full sources and licences.