What is "grey goo"

n. a hypothetical end of the world event involving nanotechnology in which out of control self-replicating nanobots consume all life on Earth

Grey goo (also spelled gray goo) is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves, a scenario that has been called ecophagy ("eating the environment", more literally "eating the habitation"). The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.

Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines or clanking replicators. The term gray goo was coined by nanotechnology pioneer Eric Drexler in his 1986 book Engines of Creation. In 2004 he stated, "I wish I had never used the term 'gray goo'." Engines of Creation mentions "gray goo" in two paragraphs and a note, while the popularized idea of gray goo was first publicized in a mass-circulation magazine, Omni, in November 1986.

Grey Goo is a science fiction real-time strategy video game developed by Petroglyph Games, produced by Six Foot, and published by Grey Box on January 23, 2015 for Microsoft Windows. It features a playable faction based on the grey goo scenario.