0-6-0 Definition

noun
Under the Whyte notation system, a simple form of steam locomotive, with three axles connecting six driving wheels, and no leading wheels or trailing wheels.
Wiktionary
Under the Whyte notation system, a steam locomotive that has six coupled driving wheels followed by two trailing wheels, with no leading wheels.
Wiktionary
Under the Whyte notation, a steam locomotive that has six coupled driving wheels followed by four trailing wheels, with no leading wheels.
Wiktionary