Useful Idioms I Have Learned from My Australian, New Zealander, and British Friends

Up your bum!
Cheers! (as in, before taking a drink)
Happy New Year! Up Your Bum, Mate!
A dag
Someone un-cool
That girl is such a dag.

Daggy
Not cool, out of fashion.
(Something I learned is that Australians tend to think that white socks, worn with anything at any time, are daggy.)
The olds
Parents
I’m going to visit the olds next month.
Do a shop
Go grocery shopping.
I really need to do a shop.
Wanker
A real idiot, a jerk.
That guy is such a wanker.
Snogging
Kissing
They were snogging all night.

Smutting
Making out
Quit your smutting!

Shagging
Having sex
Has she been shagging him?
Rocked up
Arrived at, walked up to a place.
By the time I rocked up to the shop it was closed.
Nackered
Really tired, worn out.
I was nackered by the end of the week.