Real Dictionary

aileron
countable noun: An aileron is a section on the back edge of the wing of an aircraft that can be raised or lowered in order to control the aircraft's movement.

aileron in American English
a pilot-controlled airfoil attached to, in, or near the trailing edge of an airplane wing, for controlling the rolling movements of the airplane
noun: a movable surface, usually near the trailing edge of a wing, that controls the roll of the airframe or effects maneuvers, as banks and the like

aileron in British English
noun: a flap hinged to the trailing edge of an aircraft wing to provide lateral control, as in a bank or roll