di·a·phragm 
(dīə-frăm′)
(dīə-frăm′)n.
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.
[Middle English diafragma, from Late Latin diaphragma, midriff, from Greek, partition, from diaphrassein, to barricade : dia-, intensive pref.; see DIA- + phrassein, phrag-, to enclose.]
di′a·phrag·matic (-frăg-mătĭk) adj.
di′a·phrag·mati·cal·ly adv.