college blossom 

(n) One who was considered a loser/outcast in high school, but gains a flourishing social life upon entering college.

This phenomenon is most common when said individual attended a high school filled with narrow-mindedness, immaturity, and/or all around ignorance.

Tom: Hey, isn't that the girl who used to each lunch alone in the band hall? She looks all outgoing and happy now. Even a little... sexy.

Harry: Yeah, that's Sally. She's a total college blossom. She's got guys hitting on her all the time now.

college blossom by TirraLirra December 2, 2011