This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Not known; unfamiliar: a modern-day problem unknown in earlier times.

adj. Not identified or ascertained: received flowers from an unknown admirer.

adj. Not established or verified.

adj. Not well known or widely known: an unknown artist.

n. A person or thing that is unknown: "the abyss of the unknown” ( Helena Petrovna Blavatsky).

n. A person who is not well known, as to the general public: cast an unknown in the starring role.

n. Mathematics A quantity of unknown numerical value.

adj. Not known; unidentified; not well known.

n. A variable (usually x, y or z) whose value is to be found.

n. Any fact or place about which nothing is known (as in the phrase "into the unknown").

n. A person of no identity; a nonentity

adj. Not known; not apprehended.

Not known; not become an object of knowledge; not recognized, discovered, or found out.

Unknown in this sense is often used in the predicate, followed by to: as, a man unknown to fame; a fact unknown to the public. In this use it is also often used absolntely: as, unknown to me (elliptically for it being unknown to me), he made a new contract.

Not ascertained, with relation to extent, degree, quantity, or the like; hence, incalculable; inexpressible; immense.

Not to be made known, expressed, or communicated.

Not having had sexual commerce.

n. One who or that which is unknown.

adj. not famous or acclaimed

adj. not known before

n. an unknown and unexplored region

n. a variable whose values are solutions of an equation

adj. not known to exist

adj. not known

adj. being or having an unknown or unnamed source

n. anyone who does not belong in the environment in which they are found

"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."

inglorious    unfamiliar    unsuspected    uncharted    chartless    unexplored    unidentified    unbeknown    undiagnosed    unbeknownst   

region    variable   

anonymous    obscure    stranger   

unascertained    hidden    unbeknown    undiscovered    dark    untold    incognita    incognito    terræ filius    uncharted   

Bastogne    Bayonne    Capone    Cohn    Cologne    Dijon    Goan    Joan    Leone    Malone   

new    mysterious    remote    invisible    important