1a dome-shaped muscular partition separating the thorax from the abdomen in mammals. It plays a major role in breathing, as its contraction increases the volume of the thorax and so inflates the lungs.
2a thin sheet of material forming a partition.
a taut flexible membrane in mechanical or acoustic systems.
3a thin contraceptive cap fitting over the cervix.
4a device for varying the effective aperture of the lens in a camera or other optical system.
