1. having the qualities or effects of a poison • Syn: toxicant • Similar to: toxic • Derivationally related forms: poison 2. not safe to eat • Similar to: inedible, uneatable • Derivationally related forms: poison 3. marked by deep ill will; deliberately harmful - poisonous hate - venomous criticism - vicious gossip • Syn: venomous, vicious • Similar to: malicious • Derivationally related forms: viciousness (for: vicious), venom (for: venomous), poison