Source : Webster's Revised Unabridged Dictionary (1913)

d8Gregarin91 \\"d8Greg`a*ri"n\"91\, n. pl. [NL., fr. Gregarina
   the typical genus, fr. L. gregarius. See {Gregarious}.]
   (Zo["o]l.)
   An order of Protozoa, allied to the Rhizopoda, and parasitic
   in other animals, as in the earthworm, lobster, etc. When
   adult, they have a small, wormlike body inclosing a nucleus,
   but without external organs; in one of the young stages, they
   are am[oe]biform; -- called also {Gregarinida}, and
   {Gregarinaria}.