- not known; not within the range of one's knowledge, experience, or understanding; strange; unfamiliar.
- not discovered, explored, identified, or ascertained: the unknown parts of Antarctica.
- not widely known; not famous; obscure: an unknown writer.
- a thing, influence, area, factor, or person that is unknown: the many unknowns in modern medicine; The director cast an unknown in the leading role.
- 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.
- not known, understood, or recognized
- not established, identified, or discovered
- not famous; undistinguished
- a person or thing whose action, effect, etc, is unknown or unpredictable
- an unknown person, quantity, or thing
- a variable, or the quantity it represents, the value of which is to be discovered by solving an equation; a variable in a conditional equation
