control rod

This term is a technical specification used exclusively within nuclear physics and reactor engineering. It describes a mechanical component designed to manage the criticality of a nuclear chain reaction by absorbing neutrons, thereby preventing an uncontrolled increase in power.

In a practical operational context, the movement of these rods is the primary method for adjusting the power output of a reactor or initiating an emergency shutdown, known as a scram. The term is highly specific and does not have metaphorical or casual applications in general English.