I'm sure Govtcheez was referring to definition
di·a·phragm - noun
1. Anatomy. A muscular membranous partition separating the abdominal and thoracic cavities and functioning in respiration. Also called midriff.
2. A membranous part that divides or separates.
3. A thin disk, especially in a microphone or telephone receiver, that vibrates in response to sound waves to produce electric signals, or that vibrates in response to electric signals to produce sound waves.
4. A contraceptive device consisting of a thin flexible disk, usually made of rubber, that is designed to cover the uterine cervix to prevent the entry of sperm during sexual intercourse.
5. A disk having a fixed or variable opening used to restrict the amount of light traversing a lens or optical system.