loose cannon

The phrase "loose cannon" refers to a person who is unpredictable, uncontrollable, or behaves in a reckless or irresponsible manner. It is commonly used to describe someone who acts independently without considering the consequences of their actions, therefore posing a potential danger or risk to themselves or others. The term is derived from the image of a cannon that has come loose from its mountings on a ship, potentially rolling around and causing damage.