The act of two people spreading their butt-cheeks as far as possible, placing their asses together, and making their buttholes "kiss." Farting may or may not be involved
The condition known as Dick Buttkiss occurs in severely overweight men who are already experiencing a prolonged case of "flounder dick". The flounder dick is forced to migrate so far south that it eventually locates itself right up against your butthole- resulting in a Dick Buttkiss.