diaphragm

noun Etymology: Middle English diafragma, from Late Latin diaphragma, from Greek, from diaphrassein to barricade, from dia- + phrassein to enclose Date: 14th century 1. a body partition of muscle and connective tissue; specifically the partition separating the chest and abdominal cavities in mammals 2. a dividing membrane or thin partition especially in a tube 3. a. a more or less rigid partition in the body or shell of an invertebrate b. a transverse septum in a plant stem 4. a device that limits the aperture of a lens or optical system — compare iris diaphragm 5. a thin flexible disk (as in a microphone or loudspeaker) that vibrates when struck by sound waves or that vibrates to generate sound waves 6. a molded cap usually of thin rubber fitted over the uterine cervix to act as a mechanical contraceptive barrier • diaphragmatic adjective • diaphragmatically adverb