Okay...obviously people are confused about the summer rush thing...particulraly the way it is done at schools in the Big XII North (Nebraska, K-state, KU, Mizzou being the ones where it is most prevalent). At Nebraska, KU, and KSU in particular, summer rush is pretty much the only rush.
Check my
thread about summer rush last summer for an in-depth discussion of the process. There is a pretty informative post at the top of the second page.
Here, we usually say that a guy who is given a bid (definitely coming to school here, just not enrolled) and has accepted it is "signed." It's not really a term used as a noun, just an adjative, like in "Hey this is Bob, he's signed." Officially, though that person is a pledge in the University's eye, and the bid card that's been signed by the rushee and the rush chairmen of the chapter is a binding invitation to join and be a part of that house when the school year starts.
As for a new term...for this in-limbo person...I'll say poshee, a combination of post and rushee. The term Po-Ru is also acceptable.