diaphragm

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Anatomy A muscular membranous partition separating the abdominal and thoracic cavities and functioning in respiration. Also called midriff.
2. n. A membranous part that divides or separates.
3. n. A thin disk, especially in a microphone or telephone receiver, that vibrates in response to sound waves to produce electric signals, or that vibrates in response to electric signals to produce sound waves.
4. n. A contraceptive device consisting of a thin flexible disk, usually made of rubber, that is designed to cover the uterine cervix to prevent the entry of sperm during sexual intercourse.
5. n. A disk having a fixed or variable opening used to restrict the amount of light traversing a lens or optical system.

Century Dictionary and Cyclopedia

1. n. A partition; something which divides or separates. Specifically
2. n. In mech.: A thin piece, generally of metal, serving as a partition, or for some other special purpose: as, the vibrating diaphragm of a telephone, for the communication of transmitted sounds, A ring, or a plate pierced with a circular hole so arranged as to fall in the axis of the instrument, used in optical instruments to cut off marginal beams of light, as in a camera or a telescope. Such diaphragms are often made movable, especially for photographic lenses, so that one with a large opening may be inserted when it is desired to admit abundant light to the lens, in order to use a short exposure, and one with a small opening when sharpness of detail is more desirable than shortness of exposure.
3. n. In anatomy, the midriff; the museulomembranous partition which separates the thoracic from the abdominal cavity in mammals. In man the diaphragm consists of a muscular sheet whose fibers radiate from a trefoil tendinous center to attach themselves to the lower margins of the thorax, and behind form a large bundleon cither side, called pillars of the diaphragm. The diaphragm is pierced by three principal openings: the esophageal, for the passage of the esophagus accompanied by the pneumogastric nerves; the aortic, for the passage of the aorta, thoracic duct, and large azygous vein; and the caval, for the inferior vena cava; besides some others for splanchnic nerves, etc. The diaphragm is invested on its thoracic surface by the pleural and pericardial serous membranes; on its abdominal surface by the peritoneum, a fold of which, reflected upon the liver, forms the suspensory ligament of that organ. The diaphragm is deeply concavo-convex, the convexity upward; the general figure is that of an umbrella. It is a powerful respiratory muscle, contracting at each inspiration and so flattening, while its relaxation in expiration renders it more convex; its contraction also assists in defecation and in parturition, and its spasmodic action is concerned in hiccough and sneezing; when most relaxed it rises to the level of about the fifth rib. A rudimentary diaphragm exists in birds; it is best developed in the apteryx.
4. n. In cryptogamic botany, in Equisetum, a transverse partition in the stem at the node; in Selaginella and its allies, a layer separating the prothallium from the cavity of the macrospore; in Characeæ, a constriction formed by the enveloping cells near the tip of the oögonium.
5. n. In conchology, a septum or shelf-like plate extending into the cavity of a shell, more or less partitioning it.
6. n. A thin ring or plate, pierced with a hole which is usually, but not always, circular. A series of these is attached to the inside of the tube of a telescope or other optical instrument for the purpose of preventing reflections of light from the inner walls of the tube.
7. n. A sheet or disk of flexible material, confined at the edges, but free to yield to pressure on one side or the other: used in regulating-devices where pressure is one element, and to operate valves by a pressure from a distance.
8. n. In tunnel-work, a partition separating the working-face from the first chamber.
9. n. In statistical mechanics, a portion of space, separating two ensembles of systems of molecules, such that there is no interchange of particles between the two.
10. n. In pathology, a membranous structure which partly or completely closes the lumen of a tube or cavity: as, inherited diaphragm of the larynx.
11. To interpose in the path of a beam of light, or in the field of an optical instrument, a screen containing an aperture; specifically, in photography, to reduce the aperture of an objective by the use of a diaphragm.

Wiktionary

1. n. 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; also called thoracic diaphragm.
2. n. Any of various membranes or sheets of muscle or ligament which separate one cavity from another.
3. n. A contraceptive device consisting of a flexible cup, used to cover the cervix during intercourse.
4. n. A flexible membrane separating two chambers and fixed around its periphery that distends into one or other chamber depending on the as the difference in the pressure in the chambers varies.
5. n. In a speaker, the thin, semi-rigid membrane which vibrates to produce sound.
6. n. A thin opaque structure with a central aperture, used to limit the passage of light into a camera or similar device.
7. n. A permeable or semipermeable membrane
8. n. A floor slab, metal wall panel, roof panel or the like, havig a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems.
9. v. To reduce lens aperture using an optical diaphragm.
10. v. To act as a diaphragm, for example by vibrating.

GNU Webster's 1913

1. n. A dividing membrane or thin partition, commonly with an opening through it.
2. n. The muscular and tendinous partition separating the cavity of the chest from that of the abdomen; the midriff.
3. n. A calcareous plate which divides the cavity of certain shells into two parts.
4. n. 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. n. A partition in any compartment, for various purposes.

WordNet 3.0

1. n. a mechanical device in a camera that controls size of aperture of the lens
2. n. a contraceptive device consisting of a flexible dome-shaped cup made of rubber or plastic; it is filled with spermicide and fitted over the uterine cervix
3. n. electro-acoustic transducer that vibrates to receive or produce sound waves
4. n. (anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration