(1):
(n.) A value that is nearly but not exactly correct.
(2):
(n.) A continual approach or coming nearer to a result; as, to solve an equation by approximation.
(3):
(n.) An approach to a correct estimate, calculation, or conception, or to a given quantity, quality, etc.
(4):
(n.) The act of approximating; a drawing, advancing or being near; approach; also, the result of approximating.