Source : Webster's Revised Unabridged Dictionary (1913)

Hammerhead \Ham"mer*head`\, n.
   1. (Zo["o]l.) A shark of the genus {Sphyrna} or {Zyg[ae]na},
      having the eyes set on projections from the sides of the
      head, which gives it a hammer shape. The {Sphyrna
      zyg[ae]na} is found in the North Atlantic. Called also
      {hammer fish}, and {balance fish}.

Source : WordNet®

Sphyrna zygaena
     n : fished for the hides and vitamin-rich liver [syn: {smooth
         hammerhead}]