It is used to describe a person who thinks he/she knows everything about any subject but in reality dosen't know Jack shit and is full of it 99% of the time. Taken as a reference from the online dictionary website wikipedia.
It is formed from the first Syllable of the name of person followed by ipedia. (I.E. If a person is named Kevin.. you can say Kevipedia.)
Person 2: I dunno.. let's ask ole daxipedia, he knows everything.