Definition of "Unknown" :

noun: a variable whose values are solutions of an equation

noun: an unknown and unexplored region

"They came like angels out the unknown."

noun: anyone who does not belong in the environment in which they are found

adjective: being or having an unknown or unnamed source

"A poem by an unknown author."

adjective: not known before

"Don't let anyone unknown into the house."

adjective: not famous or acclaimed

adjective: not known

"An unknown amount."

adjective: not known to exist

"Things obscurely felt surged up from unknown depths."