undo

● ● V-T If you undo something that is closed, tied, or held together, or if you undo the thing holding it, you loosen or remove the thing holding it. 打開; 解開; 鬆開

● ● V-T To undo something that has been done means to reverse its effect. 使無效

UNDO REDO 資料庫備份與恢復技術；撤消；操作上的；放棄和重做

undo flag 復原旗標；撤銷旗標；復原簽出

Oh, do let me help to undo it!

哦，讓我幫你解開它吧！

He tried to undo the knot by picking at it with his fingers.

他用手指不停地扯，想把繩結解開。

The knot was fastened in such a way that it was impossible to undo.

那個結系死了，沒法解開。

He undid the parcel.

他打開了包裹。

What's done cannot be undone.

覆水難收。

He has undone the good work of his predecessor.

他已毀了他前任取得的良好成就。