Main Entry: rud·der

Pronunciation: \ˈrə-dər\

Function: noun

Etymology: Middle English rother, from Old English rōther paddle; akin to Old English rōwan to row

Date: 14th century

1 : an underwater blade that is positioned at the stern of a boat or ship and controlled by its helm and that when turned causes the vessel's head to turn in the same direction
2 : a movable auxiliary airfoil on an airplane usually attached at the rear end that serves to control direction of flight in the horizontal plane — see airplane illustration
3 : a guiding force or strategy

— rud·der·less \-ləs\ adjective