capsule /kap″syəl, kap″səl/ pl. capsuli [L, capsula, little box] , 1. a small soluble container, usually made of gelatin, used for enclosing a dose of medication for swallowing. Compare tablet. 2. a membranous shell surrounding certain microorganisms, such as the pneumococcus bacterium. 3. a well-defined anatomical structure that encloses an organ or part, such as the capsule of the adrenal gland. Also called capsula.
