A more thorough explanation:

The major-minor fault rule is a principle in maritime law that determines fault in a collision between two vessels. If the fault of one vessel is uncontradicted and sufficient to account for the accident, then the other vessel is presumed not to have been at fault and therefore not to have contributed to the accident.

For example, if a small fishing boat collides with a large cargo ship, the fault may lie with the fishing boat for not giving way to the larger vessel. In this case, the cargo ship would be presumed not to have contributed to the accident and would not be held at fault.

However, this rule has become obsolete with the elimination of the divided-damages rule, which now allows for both vessels to be held at fault and share the cost of damages.