The Oxford Thesaurus An A-Z Dictionary of Synonyms - deadlyadj.

1) lethal, fatal; dangerous, pernicious, poisonous, noxious, toxic; baleful, harmful, nocuous: This drug is deadly if taken in large doses. 2) mortal, implacable, ruthless, savage: They were deadly enemies long after the war was over. 3 murderous, homicidal, bloodthirsty, brutal, vicious, ferocious, barbarous, barbaric, savage, inhuman, cold-blooded, heartless, ruthless, pitiless, merciless: Two deadly killers have escaped from Dartmoor prison. 4) deathly, deathlike, pale, pallid, ghostly, cadaverous, ghastly, wan, white, livid, ashen: He turned a deadly hue, as if he had seen a ghost. 5) boring, excruciating, dull, tiresome, tedious, dreary, humdrum, lacklustre, wearying, wearisome: It was a deadly play put on by deadly actors. 6) exact, precise, accurate, true, unerring, unfailing: Each arrow hit the bull's-eye with deadly accuracy.