Definition
A fixed-wing aircraft with three wings stacked vertically, one above the other, on each side of the fuselage.
Plain English
An airplane that has three wings on each side, stacked one on top of the other, instead of the usual one or two.
Context Anchor
Seen in aircraft identification, aviation history, and discussions of older aircraft designs.
Derivation
From the Latin tri- meaning 'three' and the English 'plane' (short for 'airplane,' originally referring to the flat lifting surface, or wing). So 'triplane' literally means 'three-winged.' This parallels 'biplane' (two wings) and 'monoplane' (one wing).
Why Pilots Care
Triplanes offered short wingspan and tight turning ability, but the extra drag and weight of a third wing eventually made the design obsolete. Understanding the trade-off helps explain why almost all modern aircraft are monoplanes.
Intuition Check
Do not read triplane as an airplane with three engines or three seats. The “tri” refers to three main wing levels.
Example Sentence 1
The Fokker Dr.I triplane became famous as the aircraft flown by Manfred von Richthofen, the Red Baron.
Example Sentence 2
Early aircraft designers used the triplane layout to gain extra lift from stacked wings.