1. (Noun). A viscid or sticky substance. Ooze, Sludge, Slime, Gunk.

2. sickly or cloying sentimentality.

3. A traditional sound for a baby to make.

4. An acronym for Generic Object Orientator, "a dynamic, type-based, object-oriented language in the same family as Dylan and Scheme". (See http://packages.debian.org/unstable/devel/goo.html for more).

5. chiefly Scot: A strong taste. A disagreeable smell. The Scotts also use goo to mean a liking or preference.

6. {by shortening & alter. fr. gaspergou}:
Fresh-Water Drum

7. In science fiction (and science speculation) goo refers to a mass of self-replicating nanobots. They could be good nanobots that would do stuff for us, or bad ones that would replicate until they destroyed all life on Earth. Non self-replicating nanobots are sometimes referred to as Paste. Different types of goo are identified by color (although they need not actually be the color they are named by).

  • Grey Goo (Gray Goo) refers to a gooey substance containing self-replicating nanobots that could get out of control and eat all biological matter on the planet. See Black Goo and Gold Goo for other disaster scenarios.
  • Blue goo is goo that would attack the Grey Goo, or do other useful things, like clean up the environment, fix the ozone, etc.
  • Green Goo is basically the same idea as Grey Goo, but it's made from viruses (the biological sort).
  • Khaki Goo is goo used for military purposes.
  • Red Goo is bad nano-goo, what we would call the enemy's Khaki Goo.
  • Medical Goo, obviously, is goo used for medical purposes.
  • Pink Goo is humans. That's right, I mean you. While humans aren't technically nanobots, they are self-replicating, and present a very real risk to life on the planet Earth.