The Collaborative International Dictionary of English v.0.48:

Percoid \Per"coid\ (p[~e]r"koid), a. [L. perca a perch + -oid:
   cf. F. perco["i]de.] (Zool.)
   Belonging to, or resembling, the perches, or family
   Percid[ae]. -- n. Any fish of the genus Perca, or allied
   genera of the family Percid[ae]; a percoidean.
   [1913 Webster]

WordNet (r) 3.0 (2006):

percoid
    n 1: any of numerous spiny-finned fishes of the order
         Perciformes [syn: percoid fish, percoid, percoidean]