I. ˈdedlē, -li adjective
( -er/-est )
Etymology: Middle English deedlich, deedly, from Old English dēadlīc, from dēad dead + -līc -ly — more at dead
1. obsolete
a. : subject to death
b. : being in danger of dying : likely to die
c. : inanimate
2. : tending to produce death : productive of death
among the Indians, measles, scarlatina, and whooping cough were as deadly as typhus or cholera — Willa Cather
3.
a. : aiming to kill or destroy or involving such an aim
two brave vessels matched in deadly fight — William Wordsworth
: lacking possibility of an amicable solution : implacable
a deadly quarrel
b. : tending to enervate, vitiate, or smother all force, vitality, influence, or activity
the neglect of form … was even deadlier to poetry — Peter Viereck
: extremely pernicious
the deadly effects of malicious gossip
: penetrating , devastating
containing some deadly exposure of human folly or frailty — Daniel George
4. : characteristic or suggestive of death or the dead
a deadly paleness spread over her features
5. : marked by great precision : unerring
stories hurled with deadly aim — Green Peyton
6. : marked by extreme seriousness and single-minded determination
goes in for careermanship in an impassive, deadly sort of way — James Kelly
: notably effective : unfailing
the deadly efficiency of the famed police force
: marked by complete lack of trifling or flippancy
he spoke with deadly seriousness
7. : very great : complete , extreme
a deadly silence
a deadly bore
deadly fear
Synonyms:
mortal , lethal , fatal , deathly : deadly applies to anything bound or likely to cause death
so poisonous that the drinking of it is deadly to all but serpents and hippopotami — Llewelyn Powys
Hands and his companion locked together in deadly wrestle, each with a hand upon the other's throat — R.L.Stevenson
In this sense mortal differs from deadly only in that it may occur somewhat more frequently in retrospect, in reference to situations in which death has occurred
till that young life being smitten in midheaven with mortal cold passed from her — Alfred Tennyson
lethal , the strongest word, indicates that which by its quality or quantity is designed especially to make death certain
the morphia he gave was a full lethal dose, and presently the body on the deck found peace — Nevil Shute
fatal comes between deadly and lethal in inevitability and may refer to other calamities than death
regarding strychnine, toxicology gives us a very wide range as to lethal dosage, depending on the condition and age of the patient. The average fatal dose for an adult is, I should say, two grains, though death has resulted from administrations of one grain — W.H.Wright
the fatal policy by which the Empire invited its doom while striving to avert it, the policy of matching barbarian against barbarian — J.R.Green
deathly , once a synonym for deadly , is now commonly an intensive meaning “as of death” or “resembling death”
she had a deathly fear of Quintal and with reason — C.B.Nordhoff & J.N.Hall
II. adverb
Etymology: Middle English deedliche, deedly, from Old English dēadlice, from dēadlīc, adjective
1. archaic : in a manner to occasion death : mortally : to death
the groanings of a deadly wounded man — Ezek 30:24 (Authorized Version)
2. : in an implacable manner : to the death
3. : in a manner or degree produced by or as if produced by death
turned deadly pale
4. : in a dead manner : as if dead : lifelessly
5. : extremely , excessively
deadly dull