First, a little background. In science fiction and transhumanism, 'Goo' traditionally refers to self-replicating nanobots. This started with gray goo, meaning nanobots that are programmed to replicate indefinitely, feeding off of any materials present in the environment until they exhaust all resources, leaving the Earth a teaming mass of microscopic robots. The concept was refined in short order, and black goo (nanobots designed to turn carbon dioxide into diamonds, but that get loose and eat up our atmosphere), khaki goo (goo designed for military purposes), blue goo (goo that polices other goo), and many other varieties shortly entered the literature.

By extension, pink goo refers to the wetware version of what is traditionally a hardware issue; pink goo is meat. Granted, pink goo rarely, if ever, refers to nano- anything. While technically any species of meat may be included under the pink goo umbrella, it is generally accepted that Homo sapiens is currently the most dangerous form of pink goo.

This term is credited to noted extropian Eric Watt Forste, who is said to have first used the term in August of 1997. Unfortunately, the original document where it appeared has apparently been lost to the ages (these things happen when you are approaching singularity). Regardless, this term still appears in futuristic works of many genres.
