The Collaborative International Dictionary of English v.0.48:
Unloosen \Un*loos"en\, v. t. [1st pref. un- (intensive) + loosen.] To loosen; to unloose. [1913 Webster]WordNet (r) 3.0 (2006):
unloosen v 1: grant freedom to; free from confinement [syn: free, liberate, release, unloose, unloosen, loose] [ant: confine, detain] 2: loosen the ties of; "unloose your sneakers" [syn: unloose, unloosen]