1. (身体某部分因紧张或上了年纪而)发僵，无法动弹
If a part of your body seizes up, it suddenly stops working, because you have strained it or because you are getting old.

2. (发动机等)停止运转，发生故障
If something such as an engine seizes up, it stops working, because it has not been properly cared for.