Definition of theca:
(n) :
(biology) Any of several external cases or sheaths.
(n) :
(biology, botany) The pollen-producing organ usually found in pairs and forming an anther.
(n) :
(biology, medicine) The theca folliculi: the twin layers of cells surrounding the basal lamina of an ovarian follicle.
(n) :
(biology, medicine) The thecal sac: the portion of the dura mater that surrounds the spinal cord and the cauda equina.
(n) :
(biology, microbiology, planktology) The membrane complex enveloping the cells of certain plankton including diatoms and dinoflagellates.
(n) :
(biology, marine biology) The calcareous wall of a corallite, the exoskeleton of a coral polyp.