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