LETHAL

[adjective] - able to cause or causing death; extremely dangerousThree minutes after the fire started, the house was full of lethal fumes.In the car the police found guns, knives and other lethal weapons (= weapons which can kill).A 59-year-old man was executed by lethal injection (= by having a poisonous substance put into his body) this morning.(informal) When it comes to getting what she wants, Gillian is lethal (= uses strong and determined methods).