The Collaborative International Dictionary of English v.0.48:

Calicle \Cal"i*cle\, n. [L. caliculus a small cup, dim. of
   calicis, a cup. Cf Calycle.] (Zool.)
   (a) One of the small cuplike cavities, often with elevated
       borders, covering the surface of most corals. Each is
       formed by a polyp.
   (b) One of the cuplike structures inclosing the zooids of
       certain hydroids. See Campanularian. [Written also
       calycle. See Calycle.]
       [1913 Webster]