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

The challenge of trying to place mysterious objects in space and time inspired Chu to create Anthropeum. — Emma Gometz, Scientific American, 6 July 2026

One of the most mysterious Daoist deities is the popular Perfect Warrior, or Zhenwu. — Michael Naparstek, The Conversation, 6 July 2026

Australia’s 2024 stinky ‘black balls’ incident This isn’t the first time mysterious balls were found on Australian beaches, stumping experts and locals alike. — Drew Pittock, USA Today, 8 July 2026

Nearly eight decades later, the company Thompson built (which began bearing his name after his mysterious disappearance in 1967) is still going strong. — Chris Schalkx, Travel + Leisure, 7 July 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