Declare invalid.

synonyms: annul, avoid, nullify, quash, void.

Roget 158: be impotent etc. adj.; not have a leg to stand on.    vouloir rompre l'anguille au genou [Fr.], vouloir prendre la lune avec les dents [Fr.].    collapse, faint, swoon, fall into a swoon, drop; go by the board, go by the wayside; go up in smoke, end in smoke etc. (fail) 732.    render powerless etc. adj.; deprive of power; disable, disenable^†; disarm, incapacitate, disqualify, unfit, invalidate, deaden, cramp, tie the hands; double up, prostrate, paralyze, muzzle, cripple, becripple^†, maim, lame, hamstring, draw the teeth of; throttle, strangle, garrotte, garrote; ratten^†, silence, sprain, clip the wings of, put hors de combat [Fr.], spike the guns; take the wind out of one's sails, scotch the snake, put a spoke in one's wheel; break the neck, break the back; unhinge, unfit; put out of gear.    unman, unnerve, enervate; emasculate, castrate, geld, alter, neuter, sterilize, fix.    shatter, exhaust, weaken etc. 160.    ... show more

Roget 479: confute, refute, disprove; parry, negative, controvert, rebut, confound, disconfirm, redargue^†, expose, show the fallacy of, defeat; demolish, break etc. (destroy) 162; overthrow, overturn scatter to the winds, explode, invalidate; silence; put to silence, reduce to silence; clinch an argument, clinch a question; give one a setdown^†, stop the mouth, shut up; have, have on the hip.    not leave a leg to stand on, cut the ground from under one's feet.    be confuted &c.; fail; expose one's weak point, show one's weak point.    counter evidence etc. 468.    ... show more

Roget 925: be undue etc. adj.; not be due etc. 924.    infringe, encroach, trench on, exact; arrogate, arrogate to oneself; give an inch and take an ell; stretch a point, strain a point; usurp, violate, do violence to.    disfranchise, disentitle, disqualify; invalidate.    relax etc. (be lax) 738; misbehave etc. (vice) 945; misbecome^†.    ... show more

Dutch: casseren, oblitereren, vernietigen

Make invalid for use.

synonym: cancel.

Dutch: ontkrachten

Show to be invalid.

synonym: nullify.

Take away the legal force of or render ineffective:
— Invalidate a contract.

synonyms: vitiate, void.