The Collaborative International Dictionary of English v.0.48:

choanocyte \cho"a*no*cyte`\ (k[=o]"[.a]*n[-o]*s[imac]t`;
   k[=o]*[a^]n"[-o]*s[imac]t`), n. [Gr. choa`nh funnel + -cyte.]
   any of the flagellated cells in sponges having a collar of
   cytoplasm around base of the flagellum; they maintain a flow
   of water through the body.

   Syn: collar cell.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

choanocyte
    n 1: any of the flagellated cells in sponges having a collar of
         cytoplasm around the flagellum; they maintain a flow of
         water through the body [syn: choanocyte, collar cell]