Aggro: aggravated, usually used in an accusatory sense (e.g., Don’t get aggro with me!).
Bludger: A malingering, insolent or otherwise lazy person who shirks their duties. Can also be used as an adjective in an academic context similar to “gut” (e.g., Justice is such a bludge).
Capsicum: Bell peppers.
Dodgy: This is an essential word. There is no equivalent in American English. The closest translation would be “sketchy,” but “dodgy” does not have the same lascivious undertones. Can be used to describe anything which is seedy/of poor quality/ambiguous in some way.
Esky: A cooler.
Full-on: Intense. Usually used in the construction Wow, that’s full-on.
Good onya: A tough idiom for the novice to master. Can be used as a genuine congratulatory expression, but is also occasionally used in a snide or sarcastic way in response to someone or something particularly foolish or irritating, abbreviated with a “yeah” (You spilled red wine all over my white shirt? Yeah, good onya, mate.).
Heaps: An affirmation for emphasis (e.g., I love you heaps and heaps; I have heaps of work).
Icy-pole: Ice cream or popsicle.
Jumper: Sweater—but can be both knit or jersey.
Keen: An expression denoting expertise, experience, talent (e.g., He’s a keen mathematician).
Mobile: Shortened from “mobile phone.” Can be directly substituted for “cell phone,” surprisingly enough an item equally annoying in Australia as it is across the Pacific.
Naff: A particularly good label for shooting down story ideas that seem impractical, contrived or generally silly. Can also be used to describe questionable fashion choices (implying a slightly ’80s/generally dated aesthetic). May also be used to describe OTT people if you’re feeling mean.
Ordinary: Actively terrible, but in a typically Australian vernacular quirk, the term is usually accompanied by a moderator which should not be in any way regarded as diminishing the insult (e.g., That’s a bit ordinary, isn’t it?). Note also in this example the very Australian transformation of an adamant statement into a rhetorical question.