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

What are these mysterious words, on-premise, what does this actually mean and why is this important? — Jeffrey Sonnenfeld, Fortune, 8 Sep. 2026

The film, which is seeking distribution, is set in winter 1975, when a mysterious woman crashes a holiday gathering. — ABC News, 8 Sep. 2026

This hubbub somehow awakens the mysterious powers of the titular compass, transporting the twosome to ‘Golden City’ in China, modeled after the Forbidden City, where a storyline based on Chinese mythology is about to get going. — Caspar Salmon, Variety, 5 Sep. 2026

The underwater vehicle was coasting about six feet above the ocean floor, two miles deep, when a pinkish, mysterious creature swam into its camera’s sights, drawing gasps in the research vessel floating at the surface. — Fedor Zarkhin, Los Angeles Times, 5 Sep. 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