If you describe a person or their behaviour as deadly, you mean that they will do or say anything to get what they want, without caring about other people. Deadly applies to an established or very likely cause of death. See examples of deadly used in a sentence.
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Aiming to kill or destroy; Causing or tending to cause death; Deadly, mortal, fatal, lethal mean causing or capable of causing death.
Causing or tending to cause death;
