A pill found on the floor at a rave, ravers can be a bit spacktarded and they occasionally drop pills and it's too busy to pick them up again so on a rather busy night you can often spot a few around the place.
Floor pills are both grotty and have mystery contents so are ill advised.
person A: dude here have a pill
person B: no way am I touching that, it's a floor pill you hobo.
person A: whatever
*person A necks the pill
Two hours later person A died of super bad AIDS.