diaphragm

noun

1. In mammals, a sheet of muscle separating the thorax from the abdomen, contracted and relaxed in respiration to draw air into and expel air from the lungs.

   “thoracic diaphragm”

   “pulmonary diaphragm”

2. Any of various membranes or sheets of muscle or ligament which separate one cavity from another.
3. A contraceptive device consisting of a flexible cup, used to cover the cervix during intercourse.

   “cervical diaphragm”

   “contraceptive diaphragm”

4. A flexible membrane separating two chambers and fixed around its periphery that distends into one or other chamber as the difference in the pressure in the chambers varies.

   “There also were five broken panes of glass on the two huge, rubberlike diaphragms that equalize air pressure within the dome as the artificial atmosphere expands and contracts with temperature variations, he said.”

5. In a speaker, the thin, semi-rigid membrane which vibrates to produce sound.

   “acoustic diaphragm”

6. A thin opaque structure with a central aperture, used to limit the passage of light into a camera or similar device.
7. A permeable or semipermeable membrane.

   “The mass of liquid transported through a porous diaphragm in a given time is directly proportional to the current.”

8. A floor slab, metal wall panel, roof panel or the like, having a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems.

verb

1. To reduce lens aperture using an optical diaphragm.

   “He employs an equatorial with an object-glass having a focal length of five metres, and which was diaphragmed down to eight centimetres.”

2. To act as a diaphragm, for example by vibrating.

   “The holes and burning are caused by the part diaphragming at 20000-40000 cycles/second.”