4-6-4

noun1

1. •
   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.

   • Most Canadian engines are black. [...] The C.N.R. has only three classes of non-black engines, the "6400s", the later 4-8-2s and the 4-6-4s. — 1959