Similar to a filthy Sanchez, a sexual act where one fingers one's partner's anus and then gives oneself or one's partner a mustache with the filthy finger, only much smaller and not to protrude past the width of the nose, in the style of a toothbrush mustache.
After meeting the dominatrix of his dreams at the German techno, Joel brought Frau Henrietta back to his hotel room where she concluded the night by giving him a Filthy Adolph.