1 The amount by which a ship floats lower aft than forward. Almost all ships are designed, when in proper trim, to draw slightly more water aft than forward, to aid steering and to give the rudder a slightly deeper immersion which helps to turn the ship more effectively. In the days of sail a ship with a tendency to gripe and carry excessive weather helm was eased by being trimmed down aft to give it more drag. Similarly, a ship with a tendency to pay off, needing lee helm to correct, could be improved by giving it less drag through being trimmed down forward.
2 When used as a verb, it is used to indicate that the flukes of a ship's anchor are not holding in the ground. Though the phrase to describe this is ‘the ship is dragging its anchor’—sometimes just abbreviated to the ‘the ship is dragging’—it is, of course, the anchor which is dragging.