WordNet records no synonym and no antonym for gravitate. 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.
move toward
“The conversation gravitated towards politics”
be attracted to
“Boys gravitate towards girls at that age”
move due to the pull of gravitation
“The stars gravitate towards each other”
Synonyms, antonyms and the broader and narrower relations for gravitate come from Princeton University’s WordNet. Full sources and licences.