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Synonyms

unknown quantity

Idioms  

  1. An unpredictable person or thing, as in We don't know how the new pitcher will do—he's an unknown quantity. This expression comes from algebra, where it signifies an unknown numerical value. Its figurative use dates from the mid-1800s.

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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His show premiered around the same time another unknown quantity was throwing his hat in the political ring: Donald Trump.

From Los Angeles Times ● May 20, 2026

Humphries, but the veteran is of late something of an unknown quantity.

From Los Angeles Times ● Jun. 20, 2025

Steve Witkoff is more of an unknown quantity.

From BBC ● Feb. 18, 2025

In the age of social media and endless football coverage, it is not often a player arrives at a club as a relatively unknown quantity.

From BBC ● Jan. 20, 2025

Doubleday an unknown quantity, but certainly nothing spectacular.

From "The Killer Angels: The Classic Novel of the Civil War" by Michael Shaara

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.

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