Source : Webster's Revised Unabridged Dictionary (1913)

Horsehead \Horse"head`\, n. (Zo["o]l.)
   The silver moonfish ({Selene vomer}).

Source : WordNet®

horsehead
     n : any of several silvery marine fishes with very flat bodies
         [syn: {moonfish}, {Atlantic moonfish}, {horsefish}, {horse-head},
          {dollarfish}, {Selene setapinnis}]