1historical Of a kite: having more than one flat surface (rare). Of an aircraft or its design: having two or more wings placed one above another.
See the historical note s.v. "monoplane".
Designating or relating to a technique in which several images in distinct planes or layers are used to give an enhanced impression of perspective, used especially for animated films.
3Generally. Involving or occupying several distinct planes, layers, or levels (not necessarily horizontal).
An aircraft having two or more sets of wings placed one above another (as in a biplane or triplane).
Late 19th century; earliest use found in The Century Illustrated Monthly Magazine. From multi- + plane.