1. Scene of the world's worst single gunman mass murder (37 dead), which took place in Port Arthur, Tasmania, Australia in 1996.
2. Australian equivalent of the Virginia Tech shooting, or to a lesser extent, Columbine High School Shooting.
3. Adj. To go completely insane or at least into an incomprehendable fit of anger filled rage
4. Verb. Act of extreme violence or anger
"Davo was so angry about his mrs cheating, he went completely Port Arthur on the other bloke"
"Mate, it's not that big of a deal, no need to be all Port Arthur about it."