undo

If you undo an action, you reverse it.

Example: We can undo the damage to the system.

If you undo something, unfasten it.

Example: Could you undo my buckle for me?

If you undo something in a computer program, you reverse a change done in the file.

Example: I had to undo all of the bad edits that my naughty little brother made.

An undo is a function in a computer program that can reverse a change done to a file.

Example: This program can do up to 20 undoes.