/ʌnˈdu: ||; ʌnˈdu/verb [T] (
third person singular present undoes;past tense undid;past participle undone)
1 to open sth that was tied or fastened 打开；松开；解开: to undo a knot/zip/button 松开结子；拉开拉链；解开扣子
2 to destroy the effect of sth that has already happened 使无效；取消；消除: His mistake has undone all our good work. 我们出色的工作全因他的错误而付诸东流了。