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

Derived forms: invalidates, invalidated, invalidating

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

Antonym: validate