1.AdjectiveContaining sufficient poison to be dangerous to touch or ingest.
"While highly poisonous to dogs, this substance is completely harmless if ingested by humans."
2.AdjectiveOf an animal such as a snake or spider, or parts of its body: producing a toxin intended for defensive or offensive use which is usually injected into an enemy or prey by biting or stinging; hence, of a bite or sting: injecting poison.
"Poisonous snakes should only be handled by experienced professionals."