Source : Webster's Revised Unabridged Dictionary (1913)

Tonguefish \Tongue"fish`\, n. (Zo["o]l.)
   A flounder ({Symphurus plagiusa}) native of the southern
   coast of the United States.

Source : WordNet®

tonguefish
     n : left-eyed marine flatfish whose tail tapers to a point; of
         little commercial value [syn: {tongue-fish}]