n.
Pronunciation: ' r ə -d ə r
Function: noun
Etymology: Middle English rother, from Old English r ō ther paddle; akin to Old English r ō wan 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 \ -l ə s \ adjective