global ecophagy
n. The potential destruction of life caused by rampant nanotechnological machines that break down organic matter to use as raw materials for replicating themselves.
They call it "global ecophagy". That's "eating the Earth" to you and me. Rumour has it that this is what replicating nanostructures might do, and according to one estimate, they could gobble up the entire planet in about three hours flat.
—Philip Ball, “The robot within,” New Scientist, March 15, 2003
Nanotechnologists have similarly recognized that out-of-control nanobots could destroy the biosphere; a first quantitative study of this possibility of "Global Ecophagy" by Robert Freitas was recently published in response to the article I wrote on this subject in Wired in April. His study is quite troubling, showing the clear dangers we face from unrestricted nanotechnology and the extreme difficulty and enormous scale required of any "defense."
—Bill Joy, “Genetics, nanotechnology, robotics pose danger to society,” The Sunday Patriot-News Harrisburg, July 23, 2000
2000 (earliest)
Perhaps the earliest-recognized and best-known danger of molecular nanotechnology is the risk that self-replicating nanorobots capable of functioning autonomously in the natural environment could quickly convert that natural environment (e.g., "biomass") into replicas of themselves (e.g., "nanomass") on a global basis, a scenario usually referred to as the "gray goo problem" but perhaps more properly termed "global ecophagy."
—Robert A. Freitas Jr., “Some Limits to Global Ecophagy by Biovorous Nanoreplicators, with Public Policy Recommendations,” Foresight Institute, April 01, 2000
Among the cognoscenti of nanotechnology, this threat has become known as the "gray goo problem." Though masses of uncontrolled replicators need not be gray or gooey, the term "gray goo" emphasizes that replicators able to obliterate life might be less inspiring than a single species of crabgrass. They might be superior in an evolutionary sense, but this need not make them valuable.

The gray goo threat makes one thing perfectly clear: We cannot afford certain kinds of accidents with replicating assemblers.
—K. Eric Drexler, Engines of Destruction, Engines of Creation, June 01, 1986