undo in WordNet English dictionary

1. cause to become loose
   "undo the shoelace"; "untie the knot"; "loosen the necktie"
   untie  undo  loosen 
   
2. cancel, annul, or reverse an action or its effect
   "I wish I could undo my actions"
   undo 
   
3. remove the outer cover or wrapping of
   "Let's unwrap the gifts!"; "undo the parcel"
   unwrap  undo 
   
4. deprive of certain characteristics
   unmake  undo 
   
5. cause the ruin or downfall of
   "A single mistake undid the President and he had to resign"
   undo