See more synonyms for unknown on Thesaurus.com
  1. not known; not within the range of one's knowledge, experience, or understanding; strange; unfamiliar.
  2. not discovered, explored, identified, or ascertained: the unknown parts of Antarctica.
  3. not widely known; not famous; obscure: an unknown writer.
  1. a thing, influence, area, factor, or person that is unknown: the many unknowns in modern medicine; The director cast an unknown in the leading role.
  2. Mathematics. a symbol representing an unknown quantity: in algebra, analysis, etc., frequently represented by a letter from the last part of the alphabet, as x, y, or z.

Origin of unknown

First recorded in 1250–1300, unknown is from the Middle English word unknow(e)n. See un-1, known
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for unknown

Contemporary Examples of unknown

Historical Examples of unknown

  • A few years only back, every Carolinian rode to town, and the motor was unknown.

    'Tis Sixty Years Since

    Charles Francis Adams

  • "And they come from a bitter heart," answered the unknown knight.

    The White Company

    Arthur Conan Doyle

  • Then he was but a penniless, monk-bred lad, unknown and unfriended.

    The White Company

    Arthur Conan Doyle

  • Like the Admirable Crichton, no art is to her unknown, no accomplishment by her neglected.

  • It is merely a case of not liking him less, but of liking my unknown man more.

    Her Father's Daughter

    Gene Stratton-Porter

British Dictionary definitions for unknown


  1. not known, understood, or recognized
  2. not established, identified, or discoveredan unknown island
  3. not famous; undistinguishedsome unknown artist
  4. unknown quantity a person or thing whose action, effect, etc, is unknown or unpredictable
  1. an unknown person, quantity, or thing
  2. maths a variable, or the quantity it represents, the value of which is to be discovered by solving an equation; a variable in a conditional equation3y = 4x + 5 is an equation in two unknowns
Derived Formsunknownness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for unknown

c.1300, "strange, unfamiliar" (of persons, places), from un- (1) "not" + past participle of know. Cf. Old English ungecnawen. In reference to facts, attested from early 14c. The noun meaning "unknown person" is recorded from 1590s.

Online Etymology Dictionary, © 2010 Douglas Harper