deadly

[ded-lee]

adjective

deadlier, deadliest 

1. causing or tending to cause death; fatal; lethal.

   a deadly poison.

2. aiming to kill or destroy; implacable.

   a deadly enemy.

3. like death.

   a deadly pallor.

4. excruciatingly boring.

   The dinner party was absolutely deadly.

   Synonyms: dreary, tedious, dull

5. excessive; inordinate.

   deadly haste.

6. extremely accurate.

   Annie Oakley was a deadly shot.

adverb

1. in a manner resembling or suggesting death.

   deadly pale.

2. excessively; completely.

   deadly dull.

deadly

/ ˈdɛdlɪ /

adjective

1. likely to cause death

   deadly poison

   deadly combat

2. informal,  extremely boring

adverb

1. like death in appearance or certainty

   deadly pale

   a deadly sleep

Other Word Forms

• deadliness noun
• nondeadly adjective

Word History and Origins

Origin of deadly¹

First recorded before 900; Middle English deedli(ch), Old English dēadlīce; dead, -ly

Synonym Study

See fatal.

Example Sentences

Kennedy has said he wants more studies on the COVID-19 shots, which he has long claimed are harmful — even deadly.

From Los Angeles Times

This will be the 16th outbreak of the deadly virus in the vast central African state that has poor health services, and is hit by conflict in the east.

From BBC

Natural gas is composed mostly of climate-warming methane but also contains other gases such as hydrogen sulfide, which is deadly at high concentrations.

From Salon

Border Patrol agents with a deadly or dangerous weapon — a canister of their own tear gas.

From Los Angeles Times

Last week, a Russian missile hit a block of flats in Kyiv killing 22 people, including four children, in one of the deadliest strikes since Russia's full-scale invasion.

From BBC

Related Words

• bloody 
• carcinogenic 
• cruel 
• dangerous 
• destructive 
• fatal 
• harmful 
• lethal 
• malignant 
• mortal 
• murderous 
• noxious 
• pernicious 
• poisonous 
• savage 
• suicidal 
• toxic 
• violent 
• virulent