• noun a vertical blade at the stern of a boat or ship which is used for steering
  • noun a vertical blade hinged to the tail of an aircraft, which is used for steering

Origin & History of “rudder”

Rudder comes from the same source as English row ‘use oars’ – prehistoric Germanic *- ‘steer’. Indeed it originally denoted an ‘oar used for steering’; the modern application to a fixed steering surface did not emerge until the 14th century. Its west Germanic ancestor *rōthra- also produced German ruder and Dutch roer.