Synonyms for Loosen (same or very similar meaning)
WordNet sense 1 (make less severe or strict):
relaxWordNet sense 2 (disentangle and raise the fibers of):
tease, tease apartWordNet sense 3 (cause to become loose):
undo, untieWordNet sense 4 (make loose or looser):
looseFrom the ODE community, based on WordNetadd/edit