pacific

1. (rail transport) A steam locomotive of the 4-6-2 wheel arrangement.Examples: "Britannia's firebox would appear to have derived from those of the Bulleid Pacifics, which it closely resembles."; "These were the first class of tender locomotives with this wheel arrangement in the world, although there is some doubt as to whether the name "Pacific" was given to the type because New Zealand is in the Pacific Ocean or because some similar engines were built a few months later for the Missouri Pacific Railroad."