sheer has 28 distinct synonyms spread across 6 of its 8 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
complete and without restriction or qualification; sometimes used informally as intensifiers
“absolute freedom”
so thin as to transmit light
“a hat with a diaphanous veil”
straight up or down without a break
1 of the 8 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for sheer.
Synonyms, antonyms and the broader and narrower relations for sheer come from Princeton University’s WordNet. Full sources and licences.
cause to sheer
“She sheered her car around the obstacle”