A tip drill is another name for runnin a train on a girl.
Comes from baseketball where players line up at the free throw line and tip it off the backboard consecutively, one after another.
Think of it in the sense of a group of men runnin a train on a woman. First man in line hits, next man follows until everyone has had a turn...
If the nelly song is the first time u have heard this term try listening to the lyrics more carefully. Just cause they say " it must be your ass cause its not your face" doesnt mean a tip drill is a chick with a big botty and an ugly face.
"I said it ain't no fun less we all get some
I need a tipdrill, we need a tipdrill "