diaphragm

Concise Oxford English Dictionary © 2008 Oxford University Press:
diaphragm /ˈdʌɪəfram/

▶noun

• 1 a dome-shaped muscular partition separating the thorax from the abdomen in mammals.

• 2 a thin sheet of material forming a partition.

  ■ a taut flexible membrane in mechanical or acoustic systems.

• 3 a thin contraceptive cap fitting over the cervix.

• 4 a device for varying the effective aperture of the lens in a camera or other optical system.

– derivatives
diaphragmatic adjective.

– origin ME: from late L. diaphragma, from Gk, from dia ‘through, apart’ + phragma ‘a fence’.