Meaning of undo In English

• 0 to unfasten something that is fastened or tied:

  • Can someone help me to undo my seat belt?

• 1 to remove the good or bad effects of an action or several actions:

  • I did a really tough aerobics class and then went out for dinner and undid (all) the good work!

  • It's very difficult to undo the damage that's caused by inadequate parenting in a child's early years.

• 2 to unfasten something that is closed or tied:

  • He undid the top button of his shirt and loosened his tie.

• 3 to remove the effects of something that happened earlier:

  • It’s difficult to undo the damage caused by a father who abandons his child.