\Bi"plane\, n. [Pref. bi- + plane.] (A["e]ronautics)
An a["e]roplane with two main supporting surfaces one above
the other.

\Bi"plane\, a. (A["e]ronautics)
Having, or consisting of, two superposed planes,
a["e]rocurves, or the like; of or pertaining to a biplane;
as, a biplane rudder.