diaphragm Definition

diaphragm
noun

1. anatomy.
In mammals: the sheet of muscle that separates the thorax from the abdomen.
2. optics.
An opaque disc, with a central aperture of adjustable diameter, that is used to control the amount of light entering an optical instrument such as a camera or microscope.
3. A thin vibrating disc or cone that converts sound waves to electrical signals in a microphone, or electrical signals to sound waves in a loudspeaker.
4. A cap (noun 10).

Derivative: diaphragmatic
adj

Etymology: 14c as diafragma: from Greek diaphragma partition.