fail-safe

This term is primarily used in engineering, computing, and industrial safety contexts. It describes a design philosophy where the default state of a system upon failure is the safest possible state, rather than a state that could lead to further danger. For example, a fail-safe lock on a fire door unlocks automatically when power is lost to allow evacuation.

As a noun, it refers to the specific device or protocol that implements this safety. While often used as a technical term, it is frequently applied metaphorically in business or personal planning to describe a backup plan or a "safety net" that prevents total collapse if a primary strategy fails.