a rudder is a form of:

Rudder



noun
1.
(a broad flat movable piece of wood or metal, that extends into the water at the stern of a boat or ship. By turning it the craft is steered; a like piece on the tail of an airplane, anything which guides as a bird's tail feathers) ចង្កូត (ទូកយន្ដហោះ ។ល។)
ENGLISH MEANING
noun
1.
A riddle or sieve.
2.
The mechanical appliance by means of which a vessel is guided or steered when in motion. It is a broad and flat blade made of wood or iron, with a long shank, and is fastened in an upright position, usually by one edge, to the sternpost of the vessel in such a way that it can be turned from side to side in the water by means of a tiller, wheel, or other attachment.
3.
(FIGURATIVE) That which resembles a rudder as a guide or governor; that which guides or governs the course.
4.
In an aircraft, a surface the function of which is to exert a turning moment about an axis of the craft.