pepper has 9 distinct synonyms spread across 4 of its 6 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.
climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam
any of various tropical plants of the genus Capsicum bearing peppers
pungent seasoning from the berry of the common pepper plant of East India; use whole or ground
sweet and hot varieties of fruits of plants of the genus Capsicum
Synonyms, antonyms and the broader and narrower relations for pepper come from Princeton University’s WordNet. Full sources and licences.