To unloose means to untie, unfasten, or set free from bonds or restraints. It's the opposite of tightening or securing something. When you unloose a knot in your shoelaces, you're working it free. When sailors unloose the ropes holding their boat to the dock, they're releasing them so the vessel can sail away.

The word carries a sense of deliberate releasing. You might unloose a dog from its leash so it can run freely in the park, or unloose your grip on something you've been holding tightly. In older literature, you'll sometimes find phrases like “unloose the chains” or “unloose the bonds,” meaning to free someone or something from captivity or restriction.

The word is somewhat old-fashioned and formal, so you're more likely to encounter it in classic books or poetry than in everyday conversation, where people usually just say “untie,” “loosen,” or “release.”