diaphragm

noun

1. a mechanical device in a camera that controls size of aperture of the lens"the new cameras adjust the diaphragm automatically"
2. (anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration
3. 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
4. electro-acoustic transducer that vibrates to receive or produce sound waves