WordNet records no synonym and no antonym for vice chairman. 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.
one ranking below or serving in the place of a chairman
Synonyms, antonyms and the broader and narrower relations for vice chairman come from Princeton University’s WordNet. Full sources and licences.