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 mysterious movements of money are the subject of at least one criminal proceeding in Argentina, according to court records filed in Georgia. — Antonio María Delgado, Miami Herald, 14 July 2026

Then a mysterious new player and a career-threatening injury sidelines Teresa. — John Hopewell, Variety, 14 July 2026

Stranger still is the fact these non-native fish have developed a mysterious ability to vanish for months at a time in Lake Gaston – much to the disappointment of anglers. — Mark Price, Charlotte Observer, 14 July 2026

Here’s a look back at the most infamous, shocking, blood-curdling or mysterious crimes and disasters that captured the attention of the nation — and the world. — Kori Rumore, Chicago Tribune, 13 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