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 with blood sacrifices.

—Robert Houston

mysteriousness noun

Synonyms

• cryptic
• enigmatic
• mystic
• uncanny
• enigmatical
• 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

As for Ed's other family members, his brother Henry died under mysterious circumstances in 1944. —Jordana Comiter, PEOPLE, 7 Oct. 2025

Quest for the Devil Fruit – Dodge infamous villains and escape the marines in a high-stakes race to reach a mysterious Devil Fruit ahead of the Straw Hats. —Jennifer Maas, Variety, 7 Oct. 2025

Continue reading … IN OTHER NEWS MUSK'S MYSTERY – Tesla teases mysterious announcement with cryptic videos on social media. —FOXNews.com, 7 Oct. 2025

Willem Dafoe deservedly received a Best Supporting Actor nomination for his turn as Max Schreck, the mysterious actor who played Nosferatu in Murnau's namesake film. —Declan Gallagher, Entertainment Weekly, 7 Oct. 2025

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
• cereus
• nereus
• serious
• sirius
• deleterious

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