Under the Whyte notation system, a Decapod is a steam locomotive with a 2-10-0 wheel arrangement. The design provided massive tractive effort at low speeds by putting almost all the engine's weight on the drivers, making it ideal for dragging heavy freight over steep mountain grades. Older shop men sometimes applied the term loosely to 0-10-0 switchers.
Heard on the job
The old Decapod could pull a mountain, but she beat the track to pieces if you got her over forty miles an hour.