Plain English Meaning
A long, strong beam inside the back part of a wing or tail surface. It helps the wing hold its shape under load and gives the moving control surfaces something solid to hinge from.
Full Definition
The structural beam running spanwise (from root to tip) along the rear portion of a wing or stabilizer, carrying bending and torsional loads and serving as an attachment point for control surfaces such as ailerons, flaps, or elevators.
Context Anchor
Seen in aircraft structure descriptions, especially when reading about how an is built and attached.