: not known or not well-known
also
: having an unknown value
an unknown quantity
1
: one that is not known or not well-known
especially
: a person who is little known (as to the public)
2
: something that requires discovery, identification, or clarification: such as
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
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
Alexa Dikos, Baltimore Sun, 12 Jan. 2025
Much like the series, a double homicide occurred in 2004 when an 8-year-old boy and 56-year-old woman were fatally stabbed by an unknown attacker, per The Local Sweden.
—Jordana Comiter, People.com, 10 Jan. 2025
Smithsonian Magazine, 10 Jan. 2025
One key unknown is who will lead bank supervision after Mr. Barr’s decision to step down.
—Jeanna Smialek, New York Times, 9 Jan. 2025
See all Example Sentences for unknown 
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Adjective
One male suspect with long hair in a ponytail, wearing all black clothing, is believed to have left the area in an unknown direction, according to Towson University police.
—Alexa Dikos, Baltimore Sun, 12 Jan. 2025
Much like the series, a double homicide occurred in 2004 when an 8-year-old boy and 56-year-old woman were fatally stabbed by an unknown attacker, per The Local Sweden.
—Jordana Comiter, People.com, 10 Jan. 2025
Noun
Others, though, questioned whether the potential benefits were worth the risk, particularly given the host of unknowns surrounding Covid-19, and the lack of available treatments at the time.
—Smithsonian Magazine, 10 Jan. 2025
One key unknown is who will lead bank supervision after Mr. Barr’s decision to step down.
—Jeanna Smialek, New York Times, 9 Jan. 2025
See all Example Sentences for unknown
Articles Related to unknown
Dictionary Entries Near unknown
Cite this Entry
“Unknown.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unknown. Accessed 20 Jan. 2025.
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
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