mysterious

adjective

mys·​te·​ri·​ous mi-ˈstir-ē-əs 

1

a

: of, relating to, or constituting mystery

the mysterious ways of God

b

: exciting wonder, curiosity, or surprise while baffling efforts to comprehend or identify : mystifying

heard a mysterious noise

a mysterious stranger

a mysterious plane crash

a mysterious illness

2

: stirred by or attracted to the inexplicable

… to help a mysterious wizard … ward off the end of the world …

—Robert Houston

mysteriousness noun

Synonyms of mysterious

• cryptic
• enigmatic
• mystic
• uncanny
• obscure
• dark
• deep

Examples of mysterious in a Sentence

the mysterious ways of nature

We heard a mysterious noise outside our tent.

He died under mysterious circumstances.

A mysterious illness has been spreading through the city.

There's something mysterious about that old woman.

Her behavior was very mysterious.

Recent Examples on the Web

Euclid is designed to study dark energy, the mysterious force that drives the accelerating expansion of the universe, by studying distant galaxies. — Robert Lea, Space.com, 24 June 2026

The second album this year from metalcore pioneers Converge is named for a mysterious, pulsing, low-frequency ambient drone, likened by those who hear it to a diesel engine, an idling airplane, or a kind of inescapable torture. — Alex Robert Ross, Pitchfork, 24 June 2026

The outbreak was first detected in the gold-mining town of Mongbwalu, where health workers began noticing a cluster of mysterious illnesses and deaths earlier this year. — Greg Dixon, NPR, 24 June 2026

Chopra Jonas features in the cast of his upcoming Varanasi, about a Shiva devotee who is sent on a mysterious mission to find an ancient cosmic artifact. — Georg Szalai, HollywoodReporter, 24 June 2026

Word History

Etymology

mystery entry 1 + -ous, probably after Middle French mysterieux

First Known Use

1578, in the meaning defined at sense 1a

Phrases Containing mysterious

• be mysterious

Rhymes for mysterious

• delirious
• imperious
• deleterious
• nereus
• serious
• sirius

Kids Definition

mysterious

adjective

mys·​te·​ri·​ous mis-ˈtir-ē-əs 

: containing, suggesting, or presenting a mystery

mysterious noises

also : difficult or impossible to understand

the mysterious ways of nature

mysteriously adverb