Definition & Meaning of "the coast [is] clear"

What is the origin of the idiom "the coast is clear" and when to use it?

The idiom "the coast is clear" likely originated from nautical terminology, where it referred to a situation where the sea and coastline were free from obstacles or dangers, allowing for safe passage. In its modern usage, it refers to a particular situation that is now safe or free from any potential threat, allowing someone to proceed without fear of being discovered, interrupted, or facing an obstacle.