In navigation, the instrument by which a ship is steered; that part of the helm which consists of a piece of timber, broad at the bottom, which enters the water and is attached to the stern-post by hinges, on which it turns. This timber is managed by means of the tiller or wheel.

That which guides or governs the course. For rhyme the rudder is of verses.

A sieve. Rudder perch, a small fish with the upper part of the body brown, varied with large round spots of yellow, the belly and sides streaked with lines of white and yellow. This fish is said to follow the rudders of ships in the warm parts of the Atlantic.