The Collaborative International Dictionary of English v.0.48:

Validation \Val`i*da"tion\, n. [Cf. F. validation.]
   The act of giving validity. [R.] --Knowles.
   [1913 Webster]

WordNet (r) 3.0 (2006):

validation
    n 1: the act of validating; finding or testing the truth of
         something [syn: validation, proof, substantiation]
    2: the cognitive process of establishing a valid proof [syn:
       establishment, validation]

The Free On-line Dictionary of Computing (30 December 2018):

validation

   The stage in the software life-cycle at the end of the
   development process where software is evaluated to ensure that
   it complies with the requirements.

   (1995-02-14)