DEADLINESS Synonyms: 193 Similar and Opposite Words

Q: 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

Q: 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

Q: 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

Q: 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

deadly

adjective

ˈded-lē

Definition of deadly next

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

Relevance

Antonyms & Near Antonyms

as in sheer

having no exceptions or restrictions the deadly tedium of waiting for the fog to lift

Synonyms & Similar Words

Antonyms & Near Antonyms

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

Antonyms & Near Antonyms

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

Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.

Recent Examples of deadly The deadly flies were detected in Mexico late in 2024 after years of being contained at the southern end of Panama. —

CBS News, 8 June 2026 Rock jetties can be deadly in such conditions, stay off the rocks. —

Ca Weather Bot, Sacbee.com, 8 June 2026 Officials at Robert Kerr Elementary School in Durand, Michigan, said the hat’s message could be disruptive, particularly for students who had transferred to the district after a school shooting 50 miles away in 2021, the deadliest in the state’s history. —

Maureen Groppe, USA Today, 8 June 2026 From Cold War legends to modern battlefield predators, these are seven of the deadliest helicopters ever used by military forces around the world. —

Kaif Shaikh, Interesting Engineering, 8 June 2026 See All Example Sentences for deadly

Recent Examples of Synonyms for deadly

Adjective

Hurricane Andrew — the lethal 1992 storm that almost always gets invoked as a cautionary tale — struck during a relatively quiet year and though fierce, was puny by comparison.

— Miami Herald Archives, Miami Herald, 3 June 2026
Throughout the game, players can create distractions and temporarily scare off the dinosaurs using non-lethal weaponry.

— Payton Turkeltaub, Variety, 3 June 2026