WordNet records no synonym and no antonym for stentor. 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 speaker with an unusually loud voice
the mythical Greek warrior with an unusually loud voice who died after losing a shouting contest with Hermes
any of several trumpet-shaped ciliate protozoans that are members of the genus Stentor
Synonyms, antonyms and the broader and narrower relations for stentor come from Princeton University’s WordNet. Full sources and licences.