The Collaborative International Dictionary of English v.0.48:

Copepoda \Co*pep"o*da\, n. pl. [NL., from Gr. ? an oar + -poda.]
   (Zool.)
   An order of Entomostraca, including many minute Crustacea,
   both fresh-water and marine.
   [1913 Webster]

   Note: They have a distinct carapace. The eggs are carried in
         a pair of external pouches. Some are parasites of
         fishes.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Copepoda
    n 1: minute planktonic or parasitic crustaceans [syn:
         Copepoda, subclass Copepoda]