refer has 16 distinct synonyms spread across 4 of its 7 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.
think of, regard, or classify under a subsuming principle or with a general group or in relation to another
“This plant can be referred to a known species”
use a name to designate
“Christians refer to the mother of Jesus as the Virgin Mary”
Synonyms, antonyms and the broader and narrower relations for refer come from Princeton University’s WordNet. Full sources and licences.