Pronunciation: (dī'u-fram"),[key] —n. 1. Anat. a. a muscular, membranous or ligamentous wall separating two cavities or limiting a cavity.
b. the partition separating the thoracic cavity from the abdominal cavity in mammals.
2. Physical Chem. a. a porous plate separating two liquids, as in a galvanic cell.
b. a semipermeable membrane.
3. a thin disk that vibrates when receiving or producing sound waves, as in a telephone, microphone, speaker, or the like.
4. Also called pessary. a thin, dome-shaped device, usually of rubber, for wearing over the uterine cervix during sexual intercourse to prevent conception.
5. a plate with a hole in the center or a ring that is placed on the axis of an optical instrument, as a camera, and that controls the amount of light entering the instrument.
6. a plate or web for stiffening metal-framed constructions.
—v.t. 1. to furnish with a diaphragm.
2. to reduce the aperture of (a lens, camera, etc.) by means of a diaphragm.