That uncomfortable feeling in the barber chair where the "patient" hands rub up against the barbers genitalia. It can also be the "barber" aggressively slapping an apron on a minor to "tap" his package.
Finally, barber tapping is a popular phenomenon at crowded bars in the Midwest. Particularly hanging out by the girls can.
Ronnie just Barber Tapped me while I was getting my hair cut, time to use a Flobee....
"I just barber tapped Lucy on her way to the can, did she get implants?"