Up your bum!

Very simply put, 'up your bum' is the ultimate Australian toast. It's not meant literally ('stick it up your ass and rotate', more the opposite, much like the toast: "mud in your eye". Also, it is very important to say it the right way. If you go in 'half assed' with this toast, you'll get strange looks (as an American friend of mine found out, when I recommended him to try it Queensland). Say it with a little confidence and a smile, but don't be aggressive - that's not the right way to go about things in the broad brown land of oz. Most of all - enjoy this toast with a large, cold sparkling amber beverage under the Aussie sky with a good mate.

A limey insult.
Same as the American up your ass, up yours, in your butt.
To tell someone to fuck off, get lost, go to hell.
Often accompanied by an upraised index and fore finger twisted together gesturing a upward thrusting motion.

When you're outside having sex and you're ass is facing the wind and the wind blows up your arse a bit. Like if you part your arse a bit it'll get wind up it.