Biplane /(?)/

Bi·plane

Biplane

n.
  1. An aëroplane with two main supporting surfaces one above the other. (Aëronautics)

Biplane

a.
  1. Having, or consisting of, two superposed planes, aërocurves, or the like; of or pertaining to a biplane; as, a biplane rudder. (Aëronautics)