A mass of world dominating self-reproducing nanobots. Grey goo common end-of-the-world scenario, where malfunctioning nanobots reproduce without inhibition, consuming any available raw materials.

Grey goo can also be used to describe any number of warm breakfast cereals, such as oatmeal, cream of wheat, or grits.
Man, when national labs release grey goo, I'm heading off to the mountains in Alaska before I get consumed alive.
by slackwarelinuxuser November 15, 2007
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Grey Goo is a game character from the 'Tasty Planet' series. It follows the plot of a scientist creating something that can eat dirt and clean bathrooms, but it ends up eating the whole universe. The Grey Goo first eats dirt, hops on to a hand of the scientist's assistant then eats viruses, red blood cells and white blood cells. then after being drained to a river he eats everything else.
Professor:I MADE IT
Assistant:What is it?
Professor:The Grey Goo
Assistant:What does it do?
Professor:It cleans bathrooms

2 hours later

Professor:Oh no
Assistant:RUN!!!!
by Ahyesaverylongpseudonymboi September 21, 2021
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