It is a noun used to refer to a girl that has slept with AT LEAST 4 members of Pi Lambda Phi. Some will stop at 3 just to avoid the bestowment of the term, in which case they may be referred to as "one to go".
Brochacho: One more to go as of last night.
Brodysseus: Inching close to the Pi Lam Slam, haha.
Guy #2 - Holy Shit! The skank from Zeta's party? Me too!
Guys #3, 4, 5, 6, 7 & 8 (at the same time) - ME TOO!!!!
All Guys - HELL YEAH THE BITCH GOT A PILAM SLAM DONE ON HER!!!!