any parasitic protozoan of the order Gregarinida, typically occurring in the digestive tract and body cavity of other invertebrates: phylum Apicomplexa (sporozoans)
adjective also: gregarinian (ˌɡrɛɡəˈrɪnɪən)
2.
of, relating to, or belonging to the Gregarinida
Word origin
C19: from New Latin Gregarīna genus name, from Latin gregārius; see gregarious