1. Having the qualities or effects of a poison
   "The poisonous substance was carefully handled in the laboratory";
   - toxicant
    
2. Not safe to eat; capable of causing injury or death if ingested or absorbed
   "The bright red mushrooms were poisonous"
    
3. Marked by deep ill will; deliberately harmful
   "poisonous hate";
   - venomous, vicious, viperous, malicious

See also: beady-eyed, bitchy [informal], cattish [informal], catty [informal], despiteful [archaic], inedible, leering, malevolent, spiteful, toxic, uneatable, venomed, vindictive, vixenish

Encyclopedia: Poisonous