gray goo - Computer Definition
A science fiction nightmare from "Engines of Creation, The Coming Era of Nanotechnology" by K. Eric Drexler, in which nanomachines were named "assemblers." An assembler is created from organic molecules and is designed to replicate itself. However, if something goes amiss, they could replicate until all that is left on the planet, now void of all organic matter, is "gray goo." See nanofactory.