WordNet records no synonym and no antonym for sheep. 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.
woolly usually horned ruminant mammal related to the goat
Synonyms, antonyms and the broader and narrower relations for sheep come from Princeton University’s WordNet. Full sources and licences.
a timid defenseless simpleton who is readily preyed upon
a docile and vulnerable person who would rather follow than make an independent decision
“his students followed him like sheep”