[1] : The Collaborative International Dictionary of English v.0.48

invalidate \inval"idate\, v. t. imp.  p. p. invalidated;
   p. pr.  vb. n. invalidating. from invalid null.
   to render invalid; to weaken or lessen the force of; to
   destroy the authority of; to render of no force or effect; to
   overthrow; as, to invalidate an agreement or argument.
   1913 webster
see also:
invalidated invalidating invalid 

[2] : WordNet (r) 2.0

invalidate
     v 1: declare invalid; "the contract was annulled"; "void a plea"
          syn: annul, quash, void, avoid, nullify
          ant: validate
     2: of cheques or tickets syn: cancel
     3: show to be invalid syn: nullify ant: validate
     4: take away the legal force of or render ineffective;
        "invalidateas a contract" syn: void, vitiate ant: validate
see also:
annul quash void avoid nullify validate 
cancel vitiate 

[3] : Moby Thesaurus II by Grady Ward, 1.0

61 moby thesaurus words for "invalidate":
   abate, abolish, abrogate, annihilate, annul, belie, blow sky-high,
   blow up, bring to naught, bring to nothing, buffer, cancel,
   cancel out, come to nothing, counterbalance, countermand,
   counterorder, deflate, disannul, disconfirm, discredit, disprove,
   disqualify, do away with, explode, expose, frustrate, make void,
   negate, negativate, negative, neutralize, nullify, offset,
   override, overrule, prove the contrary, puncture, quash, recall,
   recant, renege, repeal, rescind, retract, reverse, revoke,
   set aside, show up, stultify, suspend, thwart, undercut, undo,
   unfit, vacate, vitiate, void, waive, withdraw, write off

Invalidate >> I Words
Invalidate, definition of term: Invalidate
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