Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

poisonous
     adj 1: having the qualities or effects of a poison [syn: {toxicant}]
     2: not safe to eat
     3: marked by deep ill will; deliberately harmful; "a malevolent
        lie"; "poisonous hate...in his eyes"- Ernest Hemingway;
        "venomous criticism"; "vicious gossip" [syn: {venomous}, {vicious}]