undo/ʌnˋdu; ʌnˈduː/v [T] past tense undid /-ˋdId; -ˈdId/past participle undone /-ˋdʌn; -ˈdʌn/third person singular undoes /-ˋdʌz; -ˈdʌz/1 to open something that is tied, fastened, or wrapped 解开﹐松开﹐打开: He undid his shoelaces. 他解开鞋带。Have you undone all the screws? 你把所有螺丝都拧开了吗?see box at见 FASTENand 和 OPEN2 方框2 to remove the bad effects of something 消除…的坏影响: There's no way of undoing the damage done to his reputation. 他的名誉受到损害﹐已经无法挽回。