The act of rubbing ones stubbly, unshaven chin against the buttocks or around the anal area of a willing 'victim'. Named because the main participants of this pastime are wannabee boho arty types with bad skin.
Geoff: Did you see Briggsy at NG1 last night?
Ringo: Why, what happened?
Geoff: He held someone down and gave them a right good art scratching. They couldn't walk properly for the rest of the evening...