untie

verb (used with object), un·tied, un·ty·ing.

1. to loose or unfasten (anything tied); let or set loose by undoing a knot.
2. to undo the string or cords of.
3. to undo, as a cord or a knot; unknot.
4. to free from restraint.
5. to resolve, as perplexities.

verb (used without object), un·tied, un·ty·ing.

6. to become untied.

verb -ties, -tying or -tied

1. to unfasten or free (a knot or something that is tied) or (of a knot or something that is tied) to become unfastened
2. (tr) to free from constraint or restriction

v.Old English untiegan, from un- (2) + tie (v.). Related: Untied; untying.