Thing To Do, But Possibly Only In Australia Today: chiack/chyack.

It's probably best not to do this outside Australia.

In Australia, to chiack is to enjoy a bit of good-natured teasing or banter, although sometimes chiacking can turn to jeering (perhaps at an umpire, for instance).

In Britain, it's always to jeer at or deride.

It's really interesting that the word has the same nasty double-edge as the word banter, isn't it.

Thing To Do, But Possibly Only In Australia Today: chiack/chyack. Some people say this word comes from the word cheek (the word for both the part of the mouth and for insolence) from the Old English ceace, related to the Dutch kaak; some other people say it comes from the costermongers' cheery greeting chi-ike! which was also a word of praise.