I'm pretty sure it's an NPC rule that you have to be a regularly matriculated full-time student to rush and receive a bid. (Otherwise we'd be snapping up high school seniors

)
But you could have a situation where someone receives and accepts a COB in, say, November, but doesn't begin the actual new member process until the next semester. These people would be biddees. Even during formal recruitment, we'd refer to our new members as biddees until they were ribboned.
I'm confused by the whole red shirt thing... people actually chose to do this? Sounds like hazing, even though I guess it technically wouldn't be since they're not pledges...