Rack Off Meaning

(Australia, informal) To go away; to sod off.

Example: Used other than as an idiom: see rack,‎ off.
1824, Thomas Greene Fessenden, The New England Farmer, Volume 2, page 89,
  They do not, however, make use of their cider-spirit till they have racked off their cider, about the first of January.
  Rack off, hairy legs!
2002, Lydia Laube, Llama for Lunch, 2010, unnumbered page,
  The gorgeous mad Argentinian who came flying in like a whirlwind before racking off until the next day told me that my face is Argentinian. I hope that′s good.
2005, Dan Crowley, Undercover Prop, page 164,
  He came back at me with more trash talk and I said, ‘Rack off, mate. If you can′t talk sensibly to me, then scram.’
2008, Catherine Deveny, Say When, page 83,
  Like many who travel abroad, I′m constantly consumed by hatred of Australians. Loud drunken bogans whose nasal accents cut through the humid Phuket air like a chainsaw: “Jesus Chroist, Aaron, just rack off, I’ve had a gutful.”