diaphragm

noun

1. Anatomy.
   1. a muscular, membranous or ligamentous wall separating two cavities or limiting a cavity.
   2. the partition separating the thoracic cavity from the abdominal cavity in mammals.
2. Physical Chemistry.
   1. a porous plate separating two liquids, as in a galvanic cell.
   2. a semipermeable membrane.
3. a thin disk that vibrates when receiving or producing sound waves, as in a telephone, microphone, speaker, or the like.
4. Also called pessary. a thin, dome-shaped device, usually of rubber, for wearing over the uterine cervix during sexual intercourse to prevent conception.
5. a plate with a hole in the center or a ring that is placed on the axis of an optical instrument, as a camera, and that controls the amount of light entering the instrument.
6. a plate or web for stiffening metal-framed constructions.

verb (used with object)

7. to furnish with a diaphragm.
8. to reduce the aperture of (a lens, camera, etc.) by means of a diaphragm.

noun

1. anatomy any separating membrane, esp the dome-shaped muscular partition that separates the abdominal and thoracic cavities in mammalsRelated adjective: phrenic
2. a circular rubber or plastic contraceptive membrane placed over the mouth of the uterine cervix before copulation to prevent entrance of sperm
3. any thin dividing membrane
4. Also called: stop a disc with a fixed or adjustable aperture to control the amount of light or other radiation entering an optical instrument, such as a camera
5. a thin disc that vibrates when receiving or producing sound waves, used to convert sound signals to electrical signals or vice versa in telephones, etc
6. chem
   1. a porous plate or cylinder dividing an electrolytic cell, used to permit the passage of ions and prevent the mixing of products formed at the electrodes
   2. a semipermeable membrane used to separate two solutions in osmosis
7. botany a transverse plate of cells that occurs in the stems of certain aquatic plants

n.

late 14c., from Late Latin diaphragma, from Greek diaphragma “partition, barrier, muscle which divides the thorax from the abdomen,” from diaphrassein “to barricade,” from dia- “across” (see dia-) + phrassein “to fence or hedge in.” The native word is midriff. Meaning “contraceptive cap” is from 1933.

n.

1. A musculomembranous partition separating the abdominal and thoracic cavities and functioning in respiration.midriff
2. A membranous part that divides or separates.
3. 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.
4. A disk having a fixed or variable opening used to restrict the amount of light traversing a lens or optical system.

1. The large muscle that separates the chest cavity from the abdominal cavity in mammals and is the principal muscle of respiration. As the diaphragm contracts and moves downward, the lungs expand and air moves into them. As the diaphragm relaxes and moves upward, the lungs contract and air is forced out of them.
2. A thin, flexible disk, especially in a microphone or telephone receiver, that vibrates in response to sound waves to produce electrical signals, or that vibrates in response to electrical signals to produce sound waves.
3. A contraceptive device consisting of a thin flexible disk, usually made of rubber, that is designed to cover the cervix of the uterus to prevent the entry of sperm during sexual intercourse.
4. An optical device in a camera or telescope that regulates the amount of light that enters the lens or optical system. The diaphragm consists of a disk with a circular opening of variable diameter.

A dome-shaped structure made up of muscle and connective tissue that separates the abdominal cavity from the thorax and functions in respiration. By movement of the diaphragm, air is either drawn into the lungs or forced out of them.