BASF stands for Bare Ass Shrapnel Fart. To do a proper BASF one must drop one's drawers and sit, bare ass, on a hardwood floor and then rip a monster fart. The vibration of the buttcheeks against the hardwood creates a natural reverb chamber/amplifier resulting in a thunderous cacophony akin to a gunning a chainsaw while firing an M-16.
Joe's BASF (Bare Ass Shrapnel Fart) blew a hole through the parquet and now the Celtics have to playhome games at Sacred Heart until they fix it.
Basford-Day is the expression for having an extremely lazy day.
Most notably the day we will be spent in bed (Only wearing boxer shorts / underwear) watching star wars, films, playing computer games (most notably simulator games) other internet videos on a laptop while just laying there in your pit.
Guy One - What have you been up to today?
Guy Two - Absolutely Nothing
Guy One - Had a Basford-Day then?
Guy Two - Yeah