virulency

from WordNet (r) 3.0 (2006)

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

from The Collaborative International Dictionary of English v.0.48

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.
      [1913 Webster]

   2. Extreme bitterness or malignity of disposition. "Refuted
      without satirical virulency." --Barrow.
      [1913 Webster]

            The virulence of one declaimer, or the profundities
            and sublimities of the other.         --I. Taylor.
      [1913 Webster]