n. A source of all knowledge. Usually on a particular subject (e.g "The Stargate Omnipedia, "The Star Trek Omnipedia") but can theoretically be used to describe a source of literally ALL knowledge.
It is distinguished from an enclyclopedia by not needing to be short or to the point. It can include everything on the subject matter.
"What is a _____?"
"Try looking it up in the omnipedia."
A source of all human knowledge
If something isn't googlable, try looking it up in the omnipedia.