1. 拧开；旋开
If you unscrew something such as a lid, or if it unscrews, you keep turning it until you can remove it.

2. (旋出螺丝以)拆卸，取下
If you unscrew something such as a sign or mirror which is fastened to something by screws, you remove it by taking out the screws.

1. loosen something by unscrewing it

e.g. unscrew the outlet plate

2. loosen by turning

e.g. unscrew the bottle cap