From WordNet (r) 3.0 (2006):
undo
v 1: cancel, annul, or reverse an action or its effect; "I wish
I could undo my actions"
2: deprive of certain characteristics [syn: unmake, undo]
[ant: do, make]
3: cause the ruin or downfall of; "A single mistake undid the
President and he had to resign"
4: cause to become loose; "undo the shoelace"; "untie the knot";
"loosen the necktie" [syn: untie, undo, loosen]
5: remove the outer cover or wrapping of; "Let's unwrap the
gifts!"; "undo the parcel" [syn: unwrap, undo] [ant:
wrap, wrap up]