Source : Webster's Revised Unabridged Dictionary (1913)

Wolfhound \Wolf"hound`\, n. (Zo["o]l.)
   Originally, a large hound used in hunting wolves; now, any
   one of certain breeds of large dogs, some of which are nearly
   identical with the great Danes.

Source : WordNet®

wolfhound
     n : the largest breed of dogs; formerly used to hunt wolves