The elevator has a failsafe that causes it to descend slowly to the nearest floor during a power outage.

failsafe 是由 fail（失败、故障）和 safe（安全）组成的复合词，字面意思是"故障时仍能保持安全"。 failsafe 作为名词，指"自动防故障装置"，是一种安全机制，当系统出现故障时能够自动采取安全措施，防止事故发生。