sharp has 20 distinct synonyms spread across 8 of its 15 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 3 recorded opposites are dull, flat, natural.
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.
ending in a sharp point
having or demonstrating ability to recognize or draw fine distinctions
“an acute observer of politics and politicians”
keenly and painfully felt; as if caused by a sharp edge or point
“a sharp pain”
having or made by a thin edge or sharp point; suitable for cutting or piercing
“a sharp knife”
a musical notation indicating one half step higher than the note named
a long thin sewing needle with a sharp point
2 of the 15 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for sharp.
Synonyms, antonyms and the broader and narrower relations for sharp come from Princeton University’s WordNet. Full sources and licences.