Synonyms of deadly

deadly 1 of 2

adjective

ˈded-lē 

1

as in lethal

likely to cause or capable of causing death

the doctors were alarmed about the outbreak of the deadly new virus

Synonyms & Similar Words

• lethal
• fatal
• poisonous
• infectious
• infective
• killer
• harmful
• dangerous
• toxic
• murderous
• deathly
• terminal
• mortal
• destructive
• baleful
• hazardous
• injurious
• vital
• pernicious
• fell
• pestilent
• deleterious
• virulent
• baneful
• perilous
• risky
• serious
• noxious
• pestilential
• threatening
• menacing
• sublethal
• ugly
• bloody
• truculent
• unhealthy
• sanguinary
• grievous
• grave
• parlous
• unsound
• internecine
• jeopardizing
• sanguine

Antonyms & Near Antonyms

• healthy
• healthful
• beneficial
• nonfatal
• wholesome
• nonlethal
• salutary
• salubrious
• restorative
• corrective
• useful
• curative
• remedial
• advantageous
• tonic
• safe
• nontoxic
• alleviative
• nonpoisonous

2

as in sheer

having no exceptions or restrictions

the deadly tedium of waiting for the fog to lift

Synonyms & Similar Words

• sheer
• unconditional
• simple
• utter
• pure
• complete
• absolute
• total
• outright
• definite
• perfect
• damned
• damn
• very
• dreadful
• profound
• real
• huge
• downright
• endless
• crashing
• regular
• unmitigated
• thorough
• thoroughgoing
• categorical
• unadulterated
• stark
• horrible
• clean
• unqualified
• terrible
• constant
• blank
• dead
• consummate
• fair
• out-and-out
• all-out
• plumb
• blooming
• flat-out
• bodacious
• straight-out
• genuine
• eternal
• flat
• stone
• extreme
• arrant
• categoric
• rank
• unalloyed
• perpetual
• veritable
• classic
• authentic
• extraordinary
• hopeless
• unremitting
• main
• unrestricted
• undying
• frightful
• terrific
• habitual
• supreme
• confirmed
• superlative
• inveterate
• surpassing

Antonyms & Near Antonyms

• uncertain
• questionable
• doubtful
• restricted
• dubious
• qualified
• equivocal

3

as in mortal

of, relating to, or suggestive of death

a deadly pallor spread across her face as the tragic news gradually sank in

Synonyms & Similar Words

• mortal
• lethal
• dead
• spectral
• murderous
• deathly
• fatal
• mortuary
• phantom
• killer
• ghostly
• fell
• inert
• lifeless
• still
• inactive
• fateful
• quiescent
• inoperative
• cadaverous
• ghostlike
• macabre
• baleful
• pestilent

Antonyms & Near Antonyms

• active
• breathing
• live
• alive
• living
• vigorous
• vital
• animate
• energetic
• spirited
• brisk
• vivacious
• frisky
• lively
• animated
• jazzy
• well
• perky
• racy
• gay
• sprightly
• peppy
• bouncing
• whole
• springy
• healthy
• jaunty
• robust
• snappy
• pert
• sound
• spanking
• wholesome
• zippy
• sparky
• hearty
• hale
• fit
• chipper
• sprightful
• able-bodied

deadly

2 of 2

adverb

as in extremely

to a great degree

I'm deadly serious about making an offer on the house

Synonyms & Similar Words

• extremely
• incredibly
• very
• terribly
• highly
• damned
• damn
• too
• badly
• so
• severely
• super
• seriously
• really
• jolly
• desperately
• intensely
• far
• most
• that
• wildly
• wicked
• real
• such
• mighty
• full
• awful
• especially
• greatly
• exceptionally
• heavily
• much
• good and
• fiercely
• monstrous
• particularly
• awfully
• fantastically
• frightfully
• exceedingly
• exceeding
• uncommonly
• immensely
• fabulously
• passing
• roaring
• beastly
• specially
• supremely
• mortally
• extra
• absolutely
• vitally
• way
• hugely
• sore
• dang
• eminently
• surpassingly
• filthy
• utterly
• bone
• remarkably
• cracking
• rattling
• totally
• almighty
• thoroughly
• achingly
• vastly
• enormously
• thumping
• whacking
• deeply
• sorely
• completely
• positively
• blisteringly
• stinking
• archly
• spanking
• a lot
• ever
• colossally
• roaringly
• entirely
• majorly
• unco
• as all get-out
• downright
• significantly
• wholly
• corking
• mightily
• profoundly
• right
• fully
• radically
• considerably
• flat-out
• noticeably
• purely
• notably
• substantially
• visibly
• obviously
• extensively
• markedly
• excessively
• palpably
• obscenely
• monumentally
• altogether
• monstrously
• amazingly
• astonishingly
• astronomically
• staggeringly
• appreciably
• abundantly
• discernibly
• plentifully
• plainly
• grandly
• overmuch

Antonyms & Near Antonyms

• little
• somewhat
• slightly
• nominally
• negligibly
• just
• hardly
• scarcely
• barely
• minimally
• marginally
• meagerly
• scantily

Synonym Chooser

How does the adjective deadly differ from other similar words?

Some common synonyms of deadly are fatal, lethal, and mortal. While all these words mean "causing or capable of causing death," deadly applies to an established or very likely cause of death.

a deadly disease

When would fatal be a good substitute for deadly?

In some situations, the words fatal and deadly are roughly equivalent. However, fatal stresses the inevitability of what has in fact resulted in death or destruction.

fatal consequences

When is lethal a more appropriate choice than deadly?

While in some cases nearly identical to deadly, lethal applies to something that is bound to cause death or exists for the destruction of life.

lethal gas

When could mortal be used to replace deadly?

The synonyms mortal and deadly are sometimes interchangeable, but mortal implies that death has occurred or is inevitable.

a mortal wound

Example Sentences

Recent Examples of deadly

Adjective

With one of the deadliest in the sport, Cruz has preyed upon batters this season, racking up 50 strikeouts to go with a 3.26 ERA over 30.1 innings in his first season with the Yankees. —Gary Phillips, New York Daily News, 23 June 2025

The two countries have been trading deadly attacks since then, and the U.S. military has helped intercept missiles and drones fired at Israel. —Joe Hernandez, NPR, 23 June 2025

Adverb

In Oklahoma, people braced for more rain after a deluge turned deadly earlier in the weekend. —Emily Mae Czachor, CBS News, 20 Apr. 2025

However, Porziņģis' size and long-range shooting ability are the skeleton key that makes Boston's 5-out offense so deadly. —Bryan Toporek, Forbes.com, 9 May 2025