4-6-0 Definition
noun
Under the Whyte notation system, a steam locomotive that has four leading wheels on a leading truck followed by three sets of coupled driving wheels, and no trailing wheels.
Wiktionary
Under the Whyte notation system, a steam locomotive that has four coupled leading wheels, six coupled driving wheels, and a pair of trailing wheels. Also known in UK English as a "Pacific" locomotive.
Wiktionary
Under the Whyte notation system, a steam locomotive that has four leading wheels arranged in a leading truck, six coupled driving wheels and four trailing wheels in a trailing truck.
Wiktionary