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4.
A Doomtrain is an utterly leet person, and he's handsom at that :)
OMG, look at that Doomtrain, he rawks
by Beebo December 27, 2004
 
1.
1. Unstoppable. 2. Possessing great efficiency in fragging.

Applied to an individual when he is playing a video game, most likely an FPS (first-person shooter). Usually used as a noun, but can be used as an adjective or shouted by the victor of a game.
That fellow is a true Doomtrain in Halo.
by Matthew Schanuel October 03, 2007
 
2.
A special move on a video game called Gears of War created by xP I DoOm. It involves charging at an enemy with a shotgun and blasting the opponent into pieces.
That Doom Train was Sick
by KINGCOOKY April 28, 2008
 
3.
The act of smashing an item with your head, typically while intoxicated.
He doomtrained that paper towel dispenser in the bathroom.
by AG5 September 06, 2006