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

But his plans are turned upside down by a mysterious announcement signed by Lupin, that multiple museums are to be hit with simultaneous heists. — Max Goldbart, Deadline, 14 Sep. 2026

In this Dutch drama series based on Noort’s bestselling novel, four rich and glamorous couples are living the dream—until one of them dies in a mysterious house fire. — Emily Temple, Literary Hub, 14 Sep. 2026

How these birds could put on so much fat and still be healthy remains somewhat mysterious. — Rivka Galchen, New Yorker, 14 Sep. 2026

Here, the omnipresent superstar portrays Kade Auberon, a cynical rogue confronted by his mysterious past. — Jeff Spry, Space.com, 14 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