Definition of undo :
1. To bring to poverty; to impoverish; to ruin, as in reputation, morals, hopes, or the like; as, many are undone by unavoidable losses, but more undo themselves by vices and dissipation, or by indolence.
2. To loose; to open; to take to piece; to unfasten; to untie; hence, to unravel; to solve; as, to undo a knot; to undo a puzzling question; to undo a riddle.
3. To reverse, as what has been done; to annul; to bring to naught.
wash up, ruin, give away, strike, unfasten, bring out, expunge, help, spoil, strong, let on, overthrow, demolish, sex, debauch, upset, unnerve, devitalize, unbind, debilitate, wrack, discover, loose, divulge, disengage, finish, weaken, enfeeble, wipe, unbrace, slip, relax, mar, torpedo, break down, rub, unlace, enervate, sink, subvert, erase, unclasp, cross up, tease, unmake, attenuate, cross, untie, undermine, let out, continue, shatter, injure, blot, tighten, sap, bankrupt, wreck, smash, tease apart, break, unloose, vacate, unwrap, seduce, loosen, total, scratch, unsettle, unloosen, unhitch, unclose
annul (part of speech: verb)
delete, efface, divorce, eradicate, dismiss, refute, disavow, extinguish, eliminate, neutralize, repudiate, disaffirm, veto, obliterate, abnegate, negate, deny, withdraw, nullify, destroy, cancel, abolish, reject, retract, invalidate, revoke, disclaim, annul, dissolve
open (part of speech: verb)
- Ah, my soul, for such a wonder, Wilt thou not undo the door?
- For now his work I purpose to undo. - "'A Comedy of Errors' in Seven Acts", Spokeshave (AKA Old Fogy).
- When you've stood before the altar and said 'till death do us part, ' I don't see how another man, who ain't even a minister, can undo it and let you have another chance at it. - "Flower of the Dusk", Myrtle Reed.