Source : Webster's Revised Unabridged Dictionary (1913)

Virulence \Vir"u*lence\, Virulency \Vir"u*len*cy\, n. [Cf. F.
   virulence, L. virulentia an offensive odor, a stench.]
   1. The quality or state of being virulent or venomous;
      poisonousness; malignancy.

   2. Extreme bitterness or malignity of disposition. ``Refuted
      without satirical virulency.'' --Barrow.

            The virulence of one declaimer, or the profundities
            and sublimities of the other.         --I. Taylor.

Source : WordNet®

virulence
     n 1: extreme harmfulness (as the capacity of a microorganism to
          cause disease); "the virulence of the plague" [syn: {virulency}]
     2: extreme hostility; "the virulence of the malicious old man"
        [syn: {virulency}]