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
Robert Houston
mysteriousness
noun
Synonyms of mysterious
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
In 1998 two teams of astronomers announced that the expansion is accelerating, getting faster all the time, caused by a still-mysterious entity called dark energy.
—Phil Plait, Scientific American, 6 Feb. 2026
Caleb McLaughlin, who played Lucas Sinclair in Netflix’s Stranger Things, has shared his thoughts on the mysterious fate of the show’s Eleven (played by Millie Bobby Brown).
—Greg Evans, Deadline, 6 Feb. 2026
New research suggests that dark matter, the universe's most puzzling and mysterious substance, may not exist.
—Robert Lea, Space.com, 6 Feb. 2026
The first Gossip Girl book was released in 2002, debuting the cutthroat world of Manhattan's elite via a group of teens and their equally ruthless parents, all watched over by an all-seeing — and all-telling — mysterious online figure eager to spill their scandalous secrets.
—Sydney Bucksbaum, Entertainment Weekly, 5 Feb. 2026
See All Example Sentences for mysterious
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Phil Plait, Scientific American, 6 Feb. 2026
Caleb McLaughlin, who played Lucas Sinclair in Netflix’s Stranger Things, has shared his thoughts on the mysterious fate of the show’s Eleven (played by Millie Bobby Brown).
—Greg Evans, Deadline, 6 Feb. 2026
New research suggests that dark matter, the universe's most puzzling and mysterious substance, may not exist.
—Robert Lea, Space.com, 6 Feb. 2026
The first Gossip Girl book was released in 2002, debuting the cutthroat world of Manhattan's elite via a group of teens and their equally ruthless parents, all watched over by an all-seeing — and all-telling — mysterious online figure eager to spill their scandalous secrets.
—Sydney Bucksbaum, Entertainment Weekly, 5 Feb. 2026
See All Example Sentences for mysterious
Cite this Entry
“Mysterious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/mysterious. Accessed 8 Feb. 2026.
Copy CitationKids 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
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