The Collaborative International Dictionary of English v.0.48:

Validate \Val"i*date\, v. t. [See Valid.]
   To confirm; to render valid; to give legal force to.
   [1913 Webster]

         The chamber of deputies . . . refusing to validate at
         once the election of an official candidate. --London
                                                  Spectator.
   [1913 Webster]

WordNet (r) 3.0 (2006):

validate
    v 1: declare or make legally valid [syn: validate,
         formalize, formalise] [ant: annul, avoid,
         invalidate, nullify, quash, void]
    2: prove valid; show or confirm the validity of something [ant:
       invalidate, nullify]
    3: give evidence for [syn: validate, corroborate]
    4: make valid or confirm the validity of; "validate a ticket"
       [ant: invalidate, vitiate, void]