Diaphragm

Part of speech: noun (n.)

1. A dividing membrane or thin partition, commonly with an opening through it.

2. The muscular and tendinous partition separating the cavity of the chest from that of the abdomen; the midriff.

3. A calcareous plate which divides the cavity of certain shells into two parts.

4. 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. A partition in any compartment, for various purposes. Diaphragm pump, one in which a flexible diaphragm takes the place of a piston.