diaphragm has 4 distinct synonyms spread across 3 of its 4 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 mechanical device in a camera that controls size of aperture of the lens
“the new cameras adjust the diaphragm automatically”
(anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration
Synonyms, antonyms and the broader and narrower relations for diaphragm come from Princeton University’s WordNet. Full sources and licences.
a contraceptive device consisting of a flexible dome-shaped cup made of rubber or plastic; it is filled with spermicide and fitted over the uterine cervix
electro-acoustic transducer that vibrates to receive or produce sound waves