unknown

an unknown and unexplored region; "they came like angels out the unknown"

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

a variable whose values are solutions of an equation

not known; "an unknown amount"; "an unknown island"; "an unknown writer"; "an unknown source"

being or having an unknown or unnamed source; "a poem by an unknown author"; "corporations responsible to nameless owners"; "an unnamed donor"

not known to exist; "things obscurely felt surged up from unknown depths"

not famous or acclaimed; "an obscure family"; "unsung heroes of the war"

not known before; "used many strange words"; "saw many strange faces in the crowd"; "don't let anyone unknown into the house"