A brown stain found on the back of someone's underwear.
I need to reduce my carbon buttprint.
You can start by doing a better job wiping your ass.
1) The amount of carbon molecules used over a lifetime to produce and maintain a person's butt (including those used to produce contributing animal fats and to transport goods);
2) The amount of methane and other greenhouse gases produced by a person's butt over a measurable time period (e.g., a year or decade).
1) Al Gore may have reduced his carbon footprint by purchasing rainforest offsets, but his carbon buttprint remains equivalent to the annual output of a medium-sized Chinese coal-fired electrical generation facility.
2) The average US carbon buttprint is 4.6 times greater than the average buttprint of Zambia, New Guinea, or Ceylon.