fastidious has 1 distinct synonym spread across 1 of its 2 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 one recorded opposite is unfastidious.
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.
giving careful attention to detail; hard to please; excessively concerned with cleanliness
“a fastidious and incisive intellect”
having complicated nutritional requirements; especially growing only in special artificial cultures
“fastidious microorganisms”
Synonyms, antonyms and the broader and narrower relations for fastidious come from Princeton University’s WordNet. Full sources and licences.