To wipe your arse crack over your victims nose in a forward and back motion. Thus leaving a shitty smell in their nose.
Eric was so annoying that Dave gave him a bum wank.
by Afcb stu October 07, 2006
When you put your dick between a girls butt cheeks and she wanks your cock using her butt.
That slut jessica gave me a bumwank last night it was good
by Jack_Bauer January 21, 2006
like a tit wank but with your arse
kristen didn't want full anal so offered a bum wank instead
by watermelonclitlicker May 31, 2010