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

• arcane
• cryptic
• deep
• enigmatic
• enigmatical
• impenetrable
• inscrutable
• mystic
• occult
• uncanny

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

After his first game since Feb. 26, Porziņģis detailed his long journey back from a mysterious illness. —Jay King, The Athletic, 16 Mar. 2025

Everyone is a suspect, and there’s a lot of buildup to finding out what happened at a fateful St. Patrick’s Day party 15 years prior — especially when Chelsea (Ilana Glazer) makes a mysterious reference to an incident that made the entire school ostracize her. —Marianne Eloise, Vulture, 14 Mar. 2025

The film follows a teenage girl who partners with a mysterious robot and an eccentric grifter to find her brother in a dystopian future. —Julia Teti, WWD, 13 Mar. 2025

Their work is a search for meaning—an attempt to make sense of mysterious signs. —Nicolás Medina Mora, The Atlantic, 13 Mar. 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