Definition of "Mogul"

On that August Thursday afternoon, there was little freight traffic; a large "K3" Mogul went down with a short, fast goods, and a W.D. 2-8-0 proceeded northward light. […] We saw a few Gresley Moguls on goods, as a limited amount of freight traffic was sandwiched in even on this busy day.

1951 January, R. A. H. Weight, “A Railway Recorder in Essex and Hertfordshire”, in Railway Magazine, pages 44, 46