Toorak tractor, whilst described elsewhere on this listing so far, has yet to been defined as to it's origin. It originated as a piss take of the developing group of semi-affluent wankers following the fake-it-until-you-make-it rule, later to be known as a 'yuppie'. The Toorak Tractor is driven by the Toorak Cowboy, a song by The Skyhooks, a well known Australian anti-establishmentarian band of the 1970's.
The song, Toorak Cowboy, takes the piss out of the yuppie lifestyle, naturally Toorak Cowboys drive flashy vehicles to 'make up for less down below', thus 4wd's, SUV's, and even sportscars fall under the category of a Toorak Tractor.
Over the last ten years due to the origin not being as commonly heard as the term, it has come to generally mean larger more fuel consuming vehicles designed for off-road use which never see bush.
"What's a Toorak cowboy like you doing in a Lambo like that?"
"It's me Toorak Tractor mate!"