Thunder in the land down under* is a colloquial term to describe hot, passionate, energetic sex. If you've ever wanted a new term to 'spice up' your sex life, thunder in the land down under is the perfect way to describe it.
It conveys meanings of the best sexual experience one has ever had - something wild and crazy that leaves you breathless and panting, but wanting more.
*not geographically limited to sex in Australia, can be used anywhere in the world.
"Hey girl, want to come over for some thunder in the land down under?"