n. 1 a muscular partition separating the thorax from the abdomen in mammals. 2 a partition in animal and plant tissues. 3 a disc pierced by one or more holes in optical and acoustic systems etc. 4 a device for varying the effective aperture of the lens in a camera etc. 5 a thin contraceptive cap fitting over the cervix. 6 a thin sheet of material used as a partition etc. diaphragm pump a pump using a flexible diaphragm in place of a piston. diaphragmatic adj.
[ ME f. LL diaphragma f. Gk (as DIA-, phragma -atos f. phrasso fence in) ]