(v. t.) To weaken or lessen; to destroy the authority of; to render useless; as, to invalidate an agreement\ or argument.

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