1
a
: not known
It was a world and life, a way of being, utterly unknown to me.—
Avi
AviAn unknown number of cases go unreported.
For some unknown reason, the computer crashed.
b
: not well-known
an unknown writer/artist
When he left, he had been unknown. Now he was famous.—E. B. White
E. B. White2
: having an unknown value
an unknown quantity
1
a
: one that is not known or not well-known
especially
: a person who is little known (as to the public)
The director cast an unknown in the lead role.
b
the unknown
: a place, situation, or thing that is not known or understood
explorers venturing into the unknown
c
: something that is not known or not yet discovered
There are too many unknowns to go forward with the project.
2
a
: a symbol (such as x, y, or z) in a mathematical equation representing an unknown quantity
b
: a specimen (as of bacteria or mixed chemicals) required to be identified as an exercise in appropriate laboratory techniques
Synonyms of unknown
Examples of unknown in a Sentence
Adjective
a disease of unknown cause
Much remains unknown about his early life.
Her music was previously unknown outside of Asia.
An unknown number of cases go unreported.
The victim's attacker was unknown to her.
For some unknown reason, my computer crashed.
a book of unknown poems
Noun
explorers venturing off into the unknown
A fear of the unknown kept her from changing jobs.
The director cast an unknown in the lead role.
We're facing too many unknowns.
Recent Examples on the Web
Neetika Walter, Interesting Engineering, 9 Feb. 2026
One gets the sense of a man perpetually drawn to the edge of the unknown, as the boy to the edge of the sea—to questions about our primordial origins, about the etiology and eschatology of our planet, about what erodes and what endures.
—Kathryn Schulz, New Yorker, 9 Feb. 2026
Ira Winderman, Sun Sentinel, 8 Feb. 2026
Bass, 72, faces about 40 other opponents, the vast majority of them unknowns who pose little threat, though a few have the potential to break through with voters.
—David Zahniser, Los Angeles Times, 7 Feb. 2026
See All Example Sentences for unknown
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Adjective
Many of these jars contain unknown or poorly documented chemical mixtures that could be toxic to humans or harmful to the specimens themselves if disturbed.
—Neetika Walter, Interesting Engineering, 9 Feb. 2026
One gets the sense of a man perpetually drawn to the edge of the unknown, as the boy to the edge of the sea—to questions about our primordial origins, about the etiology and eschatology of our planet, about what erodes and what endures.
—Kathryn Schulz, New Yorker, 9 Feb. 2026
Noun
And there certainly have been moments when an unknown has made name for himself in the dunk contest, as has been the case with Matt McClung.
—Ira Winderman, Sun Sentinel, 8 Feb. 2026
Bass, 72, faces about 40 other opponents, the vast majority of them unknowns who pose little threat, though a few have the potential to break through with voters.
—David Zahniser, Los Angeles Times, 7 Feb. 2026
See All Example Sentences for unknown
Cite this Entry
“Unknown.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unknown. Accessed 14 Feb. 2026.
Copy CitationKids Definition
unknown
1 of 2 adjective
un·known
ˌən-ˈnōn 
: not known
also
: having an unknown value
an unknown quantity
unknown
2 of 2 noun1
: something that is unknown
2
: a symbol (as x, y, or z) representing a quantity whose value is unknown
an equation with two unknowns
Love words? Need even more definitions?
Merriam-Webster unabridged
