1. The Trunk of a Car: This is the most common meaning. Aussies use "boot" to refer to the storage compartment at the back of a car, where you put your luggage.
2. To Give Someone a Hard Time: This meaning is less common, but still used. It means to tease or pick on someone, often in a friendly way.
Example Sentences:
* "Can you put the groceries in the boot?" (meaning the trunk of the car)
* "My brother loves to boot me about my bad jokes." (meaning tease or pick on)
Keep in mind that while these are the primary meanings of "boot" in Australian English, there are other slang terms and phrases that use "boot" as well.