1. The act of being from southern Illinois. However most Chicagoans think southern illinois is springfield, but in reality it is from I-64 to mile marker 1 (cairo). It is roughly the last 100 miles of Illinios. It is where all the real OG's come from Illoinios.
2. Used to describe a person from so ill that is real, cool, gudda, etc.
1. "are we going to so ill this weekend?"
2. Frank: " Man, did you see that cat do that?"
Sceezo: "Yeah, that dude is so ill."