a bisto fart is a  fart that stains ones underwear like gravy granules, gets stronger in smell and thickens the air as it matures to full strength
"an extremely unpleasant fart that "browns", "seasons" and " thickens" all in one
"a bisto fart is a  fart that stains ones underwear like gravy granules, gets stronger in smell and thickens the air as it matures to full strength" What is the definition of "bisto fart"?