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

Away from the elections, the briefing covers a new boom in fossil fuels driven by Big Tech and the latest research on the mysterious rise of colorectal cancer among young people. — Francesca Ebel, Washington Post, 2 Nov. 2026

Early in the Brockmans’ relationship, Anna experienced a series of mysterious health mishaps. — Julia Black, Vanity Fair, 2 Nov. 2026

Then there’s his mysterious deal for Venezuelan oil, which appears to have been crafted to shield the details from public scrutiny. — Business Columnist, Los Angeles Times, 2 Nov. 2026

As familiar as a beloved family photo, her photos are also as mysterious as magic. — Olivia Kan-Sperling, Artforum, 1 Nov. 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