Di″a‐phragm (?), n. [L. diaphragma, Gr. �, fr. � to fence by a partition wall; διά through + �, �, to fence, inclose; prob. akin to L. fareire to stuff: cf. F. diaphragme. See Farce.] 1. A dividing membrane or thin partition, commonly with an opening through it.
2. (Anat.) The muscular and tendinous partition separating the cavity of the chest from that of the abdomen; the midriff.
3. (Zoöl.) A calcareous plate which divides the cavity of certain shells into two parts.
4. (Opt.) A plate with an opening, which is generally circular, used in instruments to cut off marginal portions of a beam of light, as at the focus of a telescope.
5. (Mach.) A partition in any compartment, for various purposes.
Diaphragm pump, one in which a flexible diaphragm takes the place of a piston.