unknown

being or having an unknown or unnamed source

“a poem by an unknown author”

not famous or acclaimed

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

not known before

“don't let anyone unknown into the house”

an unknown and unexplored region

“they came like angels out the unknown”

a variable whose values are solutions of an equation

not known

“an unknown amount”

not known to exist

“things obscurely felt surged up from unknown depths”