unknown

About 33.32 uses per million words.

Meaning

1. adjective Not known; unidentified; not well known.

   The concept has existed since times unknown.

2. noun A variable (usually x, y or z) whose value is to be found.
3. noun Any thing, place, or situation about which nothing is known; an unknown fact or piece of information.
4. noun A person of no identity; a nonentity.
5. verb past participle of unknow

Similar words

unidentified unknown quantity anonymous unfamiliar unheard-of undiagnosed unknowable unsung unbeknownst undiscovered

Often followed by

to in and or but quantity origin reason at

Word family

For some unknown reason the unknown unknowns