unfasten /ʌnˈfɑːsən/ ( unfastening, unfastened, unfastens )

• 1. 

  V-T If you unfasten something that is closed, tied, or held together, or if you unfasten the thing holding it, you loosen or remove the thing holding it. 解开

  例：

  When Ted was six we decided that he needed to know how to fasten and unfasten his seat belt.

  泰德六岁时，我们决定让他知道怎样系和解他的安全带。