Source : Webster's Revised Unabridged Dictionary (1913)

Aileron \Ai"le*ron\, n. [F., dim. of aile wing.]
   1. A half gable, as at the end of a penthouse or of the aisle
      of a church.

   2. (A["e]ronautics) A small plane or surface capable of being
      manipulated by the pilot of a flying machine to preserve
      or destroy lateral balance; a hinged wing tip; a lateral
      stabilizing or balancing plane.

Source : WordNet®

aileron
     n : an airfoil that controls lateral motion