screw unfasten螺丝未上紧;螺丝未上尽
To unfasten解开
unfasten nut松开螺母
to separate or unfasten使不连
Unfasten the security belt解安全带
V-T（及物动词） 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
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。