(sel), n. 1. a small room in a convent, prison, etc. 2. any small bounded area, receptacle, case, etc. 3. a small group acting as a unit within a larger organization. 4. Biol. a plant or animal streucture, usually microscopic, containing nuclear and cytoplasmic material, enclosed by a semi-permeable membrane. 5. Entomol. one of the areas into which an insect's wing is divided by the veins. 6. Embryol. an internal cavity of an ovary. 7. Bot. the pollen sac of an anther. 8. Elect. a device which generates electricity and which forms the whole or a part of, a voltaic battery. 9. Phys. Chem. a device for producing electrolysis. 10. Aeron. the gas container of a balloon. 11. Eccles. a monastery or nunnery, usually small.