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Something of an extremely disturbing nature, capable of inducing nightmares or other trauma. This is often something not meant to be disturbing. Popularized by "Mystery Science Theater 3000" and, later, James Lileks.
For some people, that S from Hell is pure nightmare fuel.
by Noah W. Smithee May 11, 2008
An idea or concept that fuels nightmares or otherwise causes extreme emotional distress. Attributed to James Lileks (www.lileks.com).
Goatse, Lemonparty and Tubgirl are pure Nightmare Fuel.

by Toytown Traveler December 11, 2006