vanilla has 1 distinct synonym spread across 1 of its 5 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.
any of numerous climbing plants of the genus Vanilla having fleshy leaves and clusters of large waxy highly fragrant white or green or topaz flowers
a flavoring prepared from vanilla beans macerated in alcohol (or imitating vanilla beans)
a distinctive fragrant flavor characteristic of vanilla beans
2 of the 5 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for vanilla.
Synonyms, antonyms and the broader and narrower relations for vanilla come from Princeton University’s WordNet. Full sources and licences.