Liberal Dictionary English Dictionary
noun
- an airplane with two sets of wings, one above and usually slightly forward of the other.
noun
- a type of aeroplane having two sets of wings, one above the otherCompare monoplane
airplane with two full wings, one above the other, 1874, as a theoretical notion; first attested 1908 in reference to the real thing; from bi- + plane (n.1). So called from the two “planes” of the double wings.