1. Capable of causing death; mortal; fatal; destructive; certain or likely to cause death; as, a deadly blow or wound.
2. Aiming or willing to destroy; implacable; desperately hostile; flagitious; as, deadly enemies. Thy assailant is quick, skillful, and deadly. (Shak)
3. Subject to death; mortal.
(Science: botany) deadly nightshade, a poisonous plant; belladonna.
Of an instrument of certain death; deadly poisons; lethal weapon; ”a lethal injection.