A rail enthusiast who follows a particular type of rail traction (for example Class 37 locomotives) and tries to travel as many miles as possible behind their chosen type of locomotive to earn the respect of fellow bashers.
They "bash" trains (travelling behind a specimen of their chosen locomotive class) for the purpose of their own enjoyment, they often lean out of windows to hear the engine noise better and often wave their arms in the air (in a manner which can confuse and send dangerous messages to railway staff) to show their appreciation of the engine hauling their train.
They are the arch-enemy of many rail staff who are not enthusiasts or bashers themselves as their exploits, can be time wasting - one wave bashers specialize in is waving his (they are rarely "hers") arm upwards to show that he does not believe the driver is applying enough power to make a suitable noise from the locomotive (despite the fact that it could damage the train if too much power was applied to quickly), this sign, to all rail staff means: "APPLY BRAKES", and this sign is often used in an emergency.
Train Driver: "I had a load of bloody bashers on the 1030, mate"
Other Train Driver: "Yeah, I had a load of them last week - had to dump the brakes because they kept waving their arms in the air"