Unknown, [uhn-nohn]
adjective
1. not known; not within the range of one's knowledge, experience, or understanding; strange; unfamiliar.
2. not discovered, explored, identified, or ascertained:
3. not widely known; not famous; obscure:
noun
4. a thing, influence, area, factor, or person that is unknown:
5. Mathematics. a symbol representing an unknown quantity: in algebra, analysis, etc., frequently represented by a letter from the last part of the alphabet, as x, y, or z.