A reference work in one or more volumes which presents extensive information in all branches of knowledge, usually arranged alphabetically. One could call it the dictionarys' older brother. Aristotle—the crazy bastard—spent a lot of his time writing up (more-or-less) encyclopaedias on all sorts of things.
But hey, who needs the definition and history of an encyclopaedia? I mean, you only need it for other knowledge so why bother reading about it's self-proclaimed definition and history when you could be doing other things, hey? Your ass is probably being wasted just reading this while your old friends are off doing important things. Don't look at me like that, you know very well what I mean.
It's OK though because none of us are real and you are the figment of your own imagination. I reckon it's time to wake up now, you've slept in.