TOFC en · ADJ Meanings (US, abbreviation, alt-of, initialism, not-comparable) Initialism of trailer on flatcar (referring to semi-trailers transported by train). alt of trailer on flatcar This explains the railroads' enthusiasm for the astonishing growth of trailer-on-flat-car traffic (T.O.F.C., or more commonly "piggyback"). 1960 November, David Morgan, “"Piggyback"—U.S. success story”, in Trains Illustrated, page 681: Relateds piggyback