Collins Chinese Dictionary Plus (3rd edition), 2011:
unfasten [
^n'f@:sn]
vt 1 [+ strap, belt, button, clothes] 解开(開) jiěkāi
2 [+ lock, latch] 打开(開) dǎkāi
在这些条目还发现'unfasten'：
在英文解释里：
open - unbar - unbind - unbuckle - unbutton - unclasp - undo - unfix - unhitch - unlatch - unstrap - untie - unyoke