unknown

(noun) an unknown and unexplored region. Synonyms: unknown region, terra incognita. Example: "They came like angels out the unknown."

(noun) anyone who does not belong in the environment in which they are found. Synonyms: stranger, alien.

(noun) a variable whose values are solutions of an equation. Synonyms: unknown quantity.

(adj) not known. Synonyms: unknown (vs. known). Examples: "An unknown amount." "An unknown island." "An unknown writer." "An unknown source."

(adj) being or having an unknown or unnamed source. Synonyms: nameless, unidentified, unnamed. Examples: "A poem by an unknown author." "Corporations responsible to nameless owners." "An unnamed donor."

(adj) not known to exist. Example: "Things obscurely felt surged up from unknown depths."

(adj) not famous or acclaimed. Synonyms: obscure, unsung. Examples: "An obscure family." "Unsung heroes of the war."

(adj) not known before. Synonyms: strange. Examples: "Used many strange words." "Saw many strange faces in the crowd." "Don't let anyone unknown into the house."