(video games, informal) A player of the video game DOOM.

Alternative letter-case form of doomer

One who believes that petroleum depletion will inevitably lead to a severe recession or depression, followed by a Malthusian catastrophe.

(neologism, sometimes capitalized) Someone who is apathetic or has a negative prospect towards the world, especially in relation to climate change.

(rare) One who, or that which, dooms.