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Verb: invalidate  in'va-li,deyt
  1. Declare invalid
    - annul, quash, void, avoid, nullify
  2. Make invalid for use
    "invalidate cheques or tickets";
    - cancel
  3. Show to be invalid
    - nullify
  4. Take away the legal force of or render ineffective
    "invalidate a contract";
    - void, vitiate

Derived forms: invalidated, invalidates, invalidating

Type of: alter, cancel, change, contradict, mark, modify, negate, score, strike down

Antonym: validate