sub·way I. \ˈsəbˌwā\noun Etymology:sub- + way 1.: an underground way or gallery: as a.: a passage under a street (as for pedestrians, electric cables, water mains) b.: a usually electric railway built partly or entirely underground and usually for local transit in metropolitan areas c.: underpass 2.: a subway train < the subway pounds along over a steel viaduct — Blake Ehrlich > II. intransitive verb (-ed/-ing/-s) : to travel by subway