The term bum blasting comes from the more well known or more commonly used term known as "bum blaster". These terms are often utilized when describing the nature of sexual intercourse between homosexual males.
"Those two homos spend all of there time bum blasting each other. Bum blasting is their life".
"Bum-Punch" the battle cry yelled before you playfully punch your partner in the bum. It only counts as a true Bum-Punch if it's yelled or sang seconds before impact.