WordNet records no synonym and no antonym for butter. 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.
an edible emulsion of fat globules made by churning milk or cream; for cooking and table use
Synonyms, antonyms and the broader and narrower relations for butter come from Princeton University’s WordNet. Full sources and licences.
a fighter who strikes the opponent with his head