neuter has 4 distinct synonyms spread across 2 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its 2 recorded opposites are masculine, feminine.
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.
having no or imperfectly developed or nonfunctional sex organs
a gender that refers chiefly (but not exclusively) to inanimate objects (neither masculine nor feminine)
Synonyms, antonyms and the broader and narrower relations for neuter come from Princeton University’s WordNet. Full sources and licences.