Noah Webster's New International Dictionary of the English Language

1. (v. t.) To make loose; to free from tightness, tension, firmness, or fixedness; to make less dense or compact; as, to loosen a string, or a knot; to loosen a rock in the earth.

2. (v. t.) To free from restraint; to set at liberty..

3. (v. t.) To remove costiveness from; to facilitate or increase the alvine discharges of.

4. (v. i.) To become loose; to become less tight, firm, or compact.