Di"a*phragm (?), n. [L.
diaphragma, Gr. &?;, fr. &?; to fence by a partition wall;
dia` 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
5. (Mach.) A partition in any
compartment, for various purposes.
Diaphragm pump, one in which a flexible
diaphragm takes the place of a piston.