vt.

1. 解开，打开；使松开；脱去（衣服等）
   He undid the parcel.

   他打开了包裹。

2. 取消，消除；使失败；使复旧
   What's done cannot be undone.

   覆水难收。

3. 破坏，败坏（成果、名誉等）；毁灭[H]
   He has undone the good work of his predecessor.

   他已毁了他前任取得的良好成就。

4. 扰乱，使不安

v.

1. unfasten, untie, or loosen.
2. cancel or reverse the effects or results of (a previous action or measure).
3. formal cause the downfall or ruin of.