loose2 [transitive] literary
to make something unpleasant begin:
And now the anger Maggie had feared was loosed.
to make something loose or to untie someone or something, especially an animal
to fire an arrow, a bullet from a gun etc
loose something on/upon somebody/somethingphrasal verb
to allow something dangerous or harmful to begin to affect a situation or other people:
the evils loosed upon humanity in World War II