A person who feels the need to act like they know it all. They are annoying to be around, and try to compensate for the fact that they are not cool in any way. When trying to prove they are more intelligent than you, they may foam in the mouth and have mini seizure.
It can also be used to refer to a person talking pure nonsense about things they have no idea about
1. Eg: this guy is such an oversabi. See him blabbing away. Yanning balls and all.
2. Eg: that guy Is such a retard.. He has been forming oversabi, and saying the eiffel tower is in Ghana. Choi!!!