Definition of "unknown" []

• Not known; unfamiliar: a modern-day problem unknown in earlier times. (adjective)
• Not identified or ascertained: received flowers from an unknown admirer. (adjective)
• Not established or verified. (adjective)
• Not well known or widely known: an unknown artist. (adjective)
• A person or thing that is unknown: "the abyss of the unknown” ( Helena Petrovna Blavatsky). (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Bailly defines it as 'the worship of the unknown, piety, godliness, humility, before the _unknown_.'"
• "The boy solves his problem in algebra, finding out the unknown quantity by those values which are given him; and can we not also infer something of the _unknown_ from the great panorama that passes unceasingly before us?"
• "Mr Rumsfeld is the man who, in February 2002, used the phrase "unknown unknowns" to describe the main dangers in any possible confrontation with Iraq."