unknown

[1]	unknown region , terra incognita
[2]	stranger , alien
[3]	unknown quantity

adj.

[1]	unrecognized , unfamiliar , strange , unnamed , anonymous , nameless , unidentified , obscure , unheard-of , little-known , humble , undistinguished , unsung
[2]	unfamiliar , unexplored , uninvestigated , unresearched , unrevealed , mysterious , uncharted , unidentified , dark
[3]	unbeknownst , untold , unrevealed
[4]	nameless , unidentified , unnamed
[5]	obscure , unsung
[6]	strange