pad has 28 distinct synonyms spread across 8 of its 11 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 number of sheets of paper fastened together along one edge
a block of absorbent material saturated with ink; used to transfer ink evenly to a rubber stamp
a flat mass of soft material used for protection, stuffing, or comfort
a platform from which rockets or space craft are launched
the fleshy cushion-like underside of an animal's foot or of a human's finger
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Synonyms, antonyms and the broader and narrower relations for pad come from Princeton University’s WordNet. Full sources and licences.