See negate in Webster's New World Roget's A-Z Thesaurus II
To make ineffective by applying an opposite force or amount:
cancel, counteract, neutralize, nullify. See actionTo put an end to, especially formally and with authority:
abolish, abrogate, annihilate, annul, cancel, invalidate, nullify, set aside, vitiate, void. (Law) extinguish. See continueTo refuse to admit the truth, reality, value, or worth of:
contradict, contravene, controvert, deny, disaffirm, gainsay, negative, oppugn. (Law) traverse. See affirmLearn more about negate