un·do 
/ˌʌnˈdu:/ verb
un·does; un·did /ˌʌnˈdu:/ verb /-ˈdɪd/ un·done /-ˈdʌn/ un·do·ing [+ obj] 1 : to open or release (something) : to unfasten or loosen (something)
▪ undo a belt/button/zipper ▪ She undid [=unbuttoned] her blouse. ▪ I can't undo [=untie] this knot. 2 : to change or stop the effect of (something) : reverse
▪ You can't undo the past. ▪ The damage cannot be undone. ▪ (computers) Will the program let me undo a change if I make a mistake? 3 formal : to cause the failure of (someone or something)
▪ He was undone by greed.
▪ undo a belt/button/zipper ▪ She undid [=unbuttoned] her blouse. ▪ I can't undo [=untie] this knot.
▪ You can't undo the past. ▪ The damage cannot be undone. ▪ (computers) Will the program let me undo a change if I make a mistake?
▪ He was undone by greed.
— see also undone
