The Collaborative International Dictionary of English v.0.48:

Pondfish \Pond"fish`\, n. (Zool.)
   Any one of numerous species of American fresh-water fishes
   belonging to the family Centrarchid[ae]; -- called also
   pond perch, and sunfish.
   [1913 Webster]

   Note: The common pondfish of New England (Lepomis gibbosus)
         is called also bream, pumpkin seed, and sunny.
         See Sunfish. The long-eared pondfish (Lepomis
         auritus) of the Eastern United States is distinguished
         by its very long opercular flap.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Moonfish \Moon"fish`\, n. (Zool.)
   (a) An American marine fish (Vomer setipennis); -- called
       also bluntnosed shiner, horsefish, and sunfish.
   (b) A broad, thin, silvery marine fish (Selene vomer); --
       called also lookdown, and silver moonfish.
   (c) The mola. See Sunfish, 1.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sunfish \Sun"fish`\, n. (Zool.)
   (a) A very large oceanic plectognath fish (Mola mola, Mola
       rotunda, or Orthagoriscus mola) having a broad body
       and a truncated tail.
   (b) Any one of numerous species of perch-like North American
       fresh-water fishes of the family Centrachidae. They
       have a broad, compressed body, and strong dorsal spines.
       Among the common species of the Eastern United States are
       Lepomis gibbosus (called also bream, pondfish,
       pumpkin seed, and sunny), the blue sunfish, or
       dollardee (Lepomis pallidus), and the long-eared
       sunfish (Lepomis auritus). Several of the species are
       called also pondfish.
   (c) The moonfish, or bluntnosed shiner.
   (d) The opah.
   (e) The basking, or liver, shark.
   (f) Any large jellyfish.
       [1913 Webster]

WordNet (r) 3.0 (2006):

sunfish
    n 1: the lean flesh of any of numerous American perch-like
         fishes of the family Centrarchidae
    2: among the largest bony fish; pelagic fish having an oval
       compressed body with high dorsal and anal fins and caudal fin
       reduced to a rudder-like lobe; worldwide in warm waters [syn:
       ocean sunfish, sunfish, mola, headfish]
    3: small carnivorous freshwater percoid fishes of North America
       usually having a laterally compressed body and metallic
       luster: crappies; black bass; bluegills; pumpkinseed [syn:
       sunfish, centrarchid]