Explicitly defined, described or recognized as a reference.
Of a religion, church etc.: formally recognized by a state as being official within that area.
Having been in existence for a long time and therefore recognized and generally accepted.
Not known; unidentified; not well known.
A variable (usually x, y or z) whose value is to be found.
A person of no identity; a nonentity
Any thing, place, or situation about which nothing is known; an unknown fact or piece of information.