The"ca (?), n.; pl. Thecae (#). [L., fr. Gr. a case to put anything in. See Tick a cover.]
1.
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.
2. Zool. (a)
The chitinous cup which protects the hydranths of certain hydroids.
(b)
The more or less cuplike calicle of a coral.
(c)
The wall forming a calicle of a coral.
© Webster 1913.