When you wipe your ass from the front and use your middle finger to snag every last particle of poo.
Mark: What do you mean you wipe your ass from the front? What the fuck is wrong with you?
Mitch: Hells ya, I gotta utilalize my drag finger!
The subtle art of dragging a gentle finger across the girls slit in order to entice and excite, with enough pressure to transfer luscious vagina odor to the fingers.
Bro: she didn't let me go all the way
Bro2: well how far did you get?
Bro: I got a drag strip finger and smelled it the rest of the day.