dead man

A dead man is someone who has died, a corpse.

The phrase often appears in expressions suggesting inevitability or doom: if someone says you're a dead man, they're threatening death or serious consequences.

In various technical contexts, a dead man is a safety device or buried anchor—a dead man's switch automatically stops a machine if the operator becomes incapacitated, and in construction, a dead man is a timber or concrete block buried to provide anchorage.