deadly /ˈdɛdli/adjective 6adverb 3forms 4 adjective6 •so dangerous that it can kill someone[…] others search for new and deadlier gases, or for soluble poisons capable of being produced in such quantities as to destroy the vegetation of whole continents […] — 1949 •(informal) Very boring.Now, at school, I was forced to sit in classes, to take notes and exams, to use textbooks that were flat, impersonal, deadly. — 2001 •Aiming or willing to destroy; implacable; desperately hostile.[…]dismount thy tucke, be yare in thy preparation, for thy assaylant is quick, skilfull and deadly. — 1601 •Very accurate (of aiming with a bow, firearm, etc.).For him the gibbet shall be built; For him the stake prepared: Him shall the scorn and wrath of men Pursue with deadly aim ; And malice, envy, spite and lies, Shall desecrate his name. — 1859 •(Ireland, informal) Excellent, awesome, cool. •(no longer used, rare) Subject to death; mortal.[…]he suffred hym selfe to be made mortall and dedly, that innocent & gyltles in hym selfe: he myght be slayne & deye for the gylty man. — 1541 adverb3 •In a way which suggests death.Her face suddenly became deadly white. •Extremely, incredibly.Though deadly weary, till spectators do / At once part and call them good boys too[…] — 1669 •(no longer used) Fatally, mortally. formsdeadlier · more deadly · deadliest · most deadly