It refers to a point in the base
system between 2nd base
and 3rd base
. It is dry-humping. It has always seemed more than simple groping but it is less than the handjobs/blowjobs of 3rd base. Dry-humping now has a definite place on the base system.
guy1: hey, y'know the base system?
guy1: wher does dry-humping go?
guy2: base 2.5
guy1: ok cool thats good to know
guy3: you guys are fucking retarded