anal sex, or the love of another mans anal area. bumbum refers to man on man sex, as they both have an arse that is "penetrable", therby being two "bums" included in the sex.
"dont try and hide it, we all know you like the bumbum"
An ice cream now available in the UK. Misperceived by many as an example of cross cultural confusion it is in fact an incisive stroke of marketing genius and a penetrating insight into the perenially adolescent mindset of the averageBrit. Who, after all, in these islands wouldn't purchase said product simply to bemuse and harass a hapless teenage vendor?
"How much for a bum bummate?"
"Make sure it's from the back of the freezer, I like bumbum best when it's hard."