warrantee has 3 distinct synonyms spread across 1 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.
a recipient of a warrant issued by a court in the United States
a customer to whom a warrant or guarantee is given
a written assurance that some product or service will be provided or will meet certain specifications
Synonyms, antonyms and the broader and narrower relations for warrantee come from Princeton University’s WordNet. Full sources and licences.