Source : Webster's Revised Unabridged Dictionary (1913)

Ferocity \Fe*roc"i*ty\, n. [L. ferocitas, fr. ferox, -ocis,
   fierce, kin to ferus wild: cf. F. ferocit['e]. See {Fierce}.]
   Savage wildness or fierceness; fury; cruelty; as, ferocity of
   countenance.

         The pride and ferocity of a Highland chief. --Macaulay.

Source : WordNet®

ferocity
     n : the property of being wild or turbulent; "the storm's
         violence" [syn: {fierceness}, {furiousness}, {fury}, {vehemence},
          {violence}, {wildness}]