look up any word, like bae:
 
1.
anal sex, and the prelude to an amusing rhyme which kids at school write on each others textbooks to get their friends in trouble:
up the bum, no harm done!

additions:
with a thumb, twice as fun!
with ya mum, watch me cum!
by me old fruity September 30, 2006
 
2.
To take someone from behind
Jazz takes Izzy up the BUM
by Jazz B (+ Mike J) March 25, 2003
 
3.
when michael takes random people (e.g his father) up the bottom
by Anonymous April 01, 2003
 
4.
The ramming of aerodynamic and not so arodynamic objects up the hrmm... anus
Everybody goes to take michael's mum up the bum while he watches in dispair.
Then he decides to go take some tall dark and hansome man up the bum in a dark alleyway, allllll night long. Bless his little gay soul