saddletankEtymologyFrom saddle + tank.nounA style of tank locomotive in which the water tank sits on top of the boiler like a saddle.“The smart little locomotives, mostly 0-6-0 saddletanks, which are always busy shunting traffic amongst the vast dockside warehouses, belong to the Manchester Ship Canal Railway, a line of considerable importance.”An early style of ballast tank submarine in which the tank sits on top like a saddle.