—adj. (deadlier, deadliest)
1 a causing or able to cause fatal injury or serious damage. b poisonous (deadly snake).
2 intense, extreme (deadly dullness).
3 (of an aim etc.) extremely accurate or effective.
4 deathlike (deadly pale; deadly faintness; deadly gloom).
5 colloq. dreary, dull.
6 implacable.
—adv.
1 like death; as if dead (deadly faint).
2 extremely, intensely (deadly serious).
Phrases and idioms:
deadly nightshade = BELLADONNA. deadly sin a sin regarded as leading to damnation, esp. pride, covetousness, lust, gluttony, envy, anger, and sloth.
Derivatives:
deadliness n.
Etymology: OE deadlic, deadlice (as DEAD, -LY(1))
Useful english dictionary. 2012.