Meaning : Cancel, annul, or reverse an action or its effect.

Example : I wish I could undo my actions.

Meaning : Deprive of certain characteristics.

Synonyms : unmake

Meaning : Cause the ruin or downfall of.

Example : A single mistake undid the President and he had to resign.

Meaning : Cause to become loose.

Example : Undo the shoelace.
Untie the knot.
Loosen the necktie.

Synonyms : loosen, untie

Meaning : Remove the outer cover or wrapping of.

Example : Let's unwrap the gifts!.
Undo the parcel.

Synonyms : unwrap