The Collaborative International Dictionary of English v.0.48:

Poisonous \Poi"son*ous\, a.
   Having the qualities or effects of poison; venomous; baneful;
   corrupting; noxious. --Shak. -- Poi"son*ous*ly, adv. --
   Poi"son*ous*ness, n.
   [1913 Webster]