monkfish has 10 distinct synonyms spread across 2 of its 3 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.
flesh of a large-headed anglerfish of the Atlantic waters of North America
fishes having large mouths with a wormlike filament attached for luring prey
sharks with broad flat bodies and winglike pectoral fins but that swim the way sharks do
Synonyms, antonyms and the broader and narrower relations for monkfish come from Princeton University’s WordNet. Full sources and licences.