Definition:
- (n.) A sheath; a case; as, the theca, or cell, of an anther; the theca, or spore case, of a fungus; the theca of the spinal cord.
- (n.) The chitinous cup which protects the hydranths of certain hydroids.
- (n.) The more or less cuplike calicle of a coral.
- (n.) The wall forming a calicle of a coral.