Pronunciation: (ves'i-kul), [key]
1. a small sac or cyst.
2. Biol.a small bladderlike cavity, esp. one filled with fluid.
3. Pathol.a circumscribed elevation of the epidermis containing serous fluid; blister.
4. Geol.a small, usually spherical cavity in a rock or mineral, formed by expansion of a gas or vapor before the enclosing body solidified.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.