The Collaborative International Dictionary of English v.0.48:

Grouper \Group"er\, n. [Corrupted fr. Pg. garupa crupper. Cf.
   Garbupa.] (Zool.)
   (a) One of several species of valuable food fishes of the
       genus Epinephelus, of the family Serranid[ae], as the
       red grouper, or brown snapper (Epinephelus morio), and
       the black grouper, or warsaw (Epinephelus nigritus),
       both from Florida and the Gulf of Mexico.
   (b) The tripletail (Lobotes).
   (c) In California, the name is often applied to the
       rockfishes. [Written also groper, gruper, and
       trooper.]
       [1913 Webster]