<p><strong>Noun</strong></p><ul><li>Anatomy: a muscular, membranous or ligamentous wall separating two cavities or limiting a cavity</li><li>the partition separating the thoracic cavity from the abdominal cavity in mammals</li><li>Physical Chemistry: a porous plate separating two liquids, as in a galvanic cell</li><li>a semipermeable membrane</li><li>a thin disk that vibrates when receiving or producing sound waves, as in a telephone, microphone, speaker, or the like</li><li>also called pessary: a thin, dome-shaped device, usually of rubber, for wearing over the uterine cervix during sexual intercourse to prevent conception</li><li>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</li><li>a plate or web for stiffening metal-framed constructions</li></ul><p><strong>Verb</strong></p><ul><li>to furnish with a diaphragm</li><li>to reduce the aperture of (a lens, camera, etc.) by means of a diaphragm</li></ul>