Source : Webster's Revised Unabridged Dictionary (1913)

Fierce \Fierce\, a. [Compar. {Fiercer}; superl. {Fiercest}.]
   [OE. fers, fiers, OF. fier, nom. fiers, fierce, savage,
   cruel, F. fier proud, from L. ferus wild, savage, cruel;
   perh. akin to E. bear the animal. Cf. {Feral}, {Ferocity}.]
   1. Furious; violent; unrestrained; impetuous; as, a fierce
      wind.

            His fierce thunder drove us to the deep. --Milton.

   2. Vehement in anger or cruelty; ready or eager to kill or
      injure; of a nature to inspire terror; ferocious. ``A
      fierce whisper.'' --Dickens. ``A fierce tyrant.'' --Pope.

            The fierce foe hung upon our broken rear. --Milton.

            Thou huntest me as a fierce lion.     --Job. x. 16.

   3. Excessively earnest, eager, or ardent.

   Syn: Ferocious; savage; cruel; vehement; impetuous;
        barbarous; fell. See {Ferocious}. -- {Fierce"ly}, adv.
        -- {Fierce"ness}, n.

Source : WordNet®

fierce
     adj 1: marked by extreme and violent energy; "a ferocious beating";
            "fierce fighting"; "a furious battle" [syn: {ferocious},
             {furious}, {savage}]
     2: marked by extreme intensity of emotions or convictions;
        inclined to react violently; fervid; "fierce loyalty"; "in
        a tearing rage"; "vehement dislike"; "violent passions"
        [syn: {tearing}, {vehement}, {violent}, {trigger-happy}]
     3: ruthless in competition; "cutthroat competition"; "bowelless
        readiness to take advantage" [syn: {cutthroat}, {bowelless}]
     4: violently agitated and turbulent; "boisterous winds and
        waves"; "the fierce thunders roar me their music"- Ezra
        Pound; "rough weather"; "rough seas" [syn: {boisterous}, {rough}]