Plain English Meaning
A skeleton of metal tubes or wooden bars welded or bolted into triangles, with a fabric or light metal cover stretched over it. The triangle frame holds the aircraft together; the cover does not.
Full Definition
An aircraft fuselage construction method in which the airframe is built from a framework of rigid members — typically steel tubes or wooden beams — joined at the ends to form triangular shapes that carry the structural loads. The outer surface (fabric or thin metal) is non-load-bearing and only provides shape and aerodynamic skin.
Context Anchor
Seen in aircraft construction discussions, especially when describing older, light, or fabric-covered airplanes with tube-and-fabric fuselages.