Vi"per*ous*ly

from The Collaborative International Dictionary of English v.0.48

Viperous \Vi"per*ous\, a.
   Having the qualities of a viper; malignant; venomous; as, a
   viperous tongue. "This viperous slander." --Shak. --
   {Vi"per*ous*ly}, adv.
   [1913 Webster]