The NAVIGATION RULES define a "vessel not under command" as a vessel which __________.

A "vessel not under command" refers specifically to a vessel that is unable to maneuver as required by the navigation rules due to circumstances beyond its control. This condition indicates that the vessel cannot comply with the normal navigation regulations, which is critical for maintaining safety on the water. Such vessels may not be able to take action to avoid collisions or change their course and speed as they normally would.

While a vessel malfunctioning, losing power, or conducting maintenance might seem related, they do not encompass the broader definition required by the navigation rules. A vessel that has lost power may fall under the category of being "not under command," but it is the inability to maneuver according to the rules that precisely defines the status, making this the most accurate and complete description of a "vessel not under command."