Source : Webster's Revised Unabridged Dictionary (1913)

Sunfish \Sun"fish`\, n. (Zo["o]l.)
   (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 {Centrachid[ae]}. 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 ({L. pallidus}), and the long-eared sunfish
       ({L. 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.

Source : WordNet®

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}, {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:
         {centrarchid}]
     [also: {sunfishes} (pl)]