Definition of deadly adjective from the Oxford Advanced Learner's Dictionary

     

    deadly

     adjective
    adjective
    BrE BrE//ˈdedli//
     
    ; NAmE NAmE//ˈdedli//
     
    (deadlier, deadliest)More deadly and deadliest are the usual forms. You can also use most deadly. Boredom
     
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  1. 1causing or likely to cause death synonym lethal a deadly weapon/disease deadly poison The cobra is one of the world's deadliest snakes. The terrorists have chosen to play a deadly game with the civilian population.
  2. 2[only before noun] extreme; complete I'm in deadly earnest. We sat in deadly silence. They are deadly enemies (= are full of hatred for each other).
  3. 3extremely effective, so that no defence is possible His aim is deadly (= so accurate that he can kill easily). It was the deadly striker's 11th goal of the season.
  4. 4(informal) very boring The lecture was absolutely deadly. See related entries: Boredom
  5. Word Origin Old English dēadlīc ‘mortal, in danger of death’ (see dead, -ly).Extra examples The loss of skills training was deadly for the economy. The man possessed an absolutely deadly charm. This poison is potentially deadly. Antimony is a deadly poison. He was charged with possession of a deadly weapon. Her aim with a gun was deadly. It was the deadly striker’s 11th goal of the season. The cobra is one of the world’s deadliest snakes. The missile found its target with deadly accuracy.
See the Oxford Advanced American Dictionary entry: deadly