A command included in many word processing and graphics software applications that allows a user to eliminate or reverse the last action. For example, say you've just applied a moustache to the Mona Lisa with your new paint program. You then decide you like the painting better the way it was originally. With a click of the undo button or command, the moustache is gone. In many Windows compatible programs, pressing the Ctrl and Z keys together will accomplish the same thing as the undo feature.
Undo is a command in most creative programs. It erases the last change done to the document reverting it back to an older state. In some more advanced programs such as graphic processing, undo will negate the last command done to the file being edited.
To bring to poverty; to impoverish; to ruin, as in reputation, morals, hopes, or the like; as, many are undone by unavoidable losses, but more undo themselves by vices and dissipation, or by indolence.