Australian: The sudden and abrupt switching of tone, mood, or emotional expression to one that is the complete opposite of the preceding state, often occurring without a gradual transition and creating a stark emotional contrast. The term is derived from the speaking style of Bob Katter, whose public appearances are noted for sudden shifts in tone or emotion - behaviour that inspired the verb “to katter” and the noun “kattering.”
Yeah nah it was completely ridiculous, he was fine one second and then he just started kattering... Oh, look! The blossoms have started blooming!
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.