haddock 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. 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.
lean white flesh of fish similar to but smaller than cod; usually baked or poached or as fillets sauteed or fried
important food fish on both sides of the Atlantic; related to cod but usually smaller
Synonyms, antonyms and the broader and narrower relations for haddock come from Princeton University’s WordNet. Full sources and licences.