Australian phrase:
1. A phrase used when a person tells you something which is clearly exaggerated or a lie, and you want them to know that you don’t believe them.

2. A phrased used to tell a male to get his hand off of his genitals, or stop masturbating.

When you eat dirt for the first time and leave your family to build a shack in the woods

Another way of saying, "As if!!" or "Your full of it."