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8.
A derogatory term for Americans, originally a word play on "yank" rhyming with septic tank, shortened to "seppo". The term became popular among the British and the Australians around the time of WWII, when American soldiers were staged in both respective countries on the way to battle in Europe and Asia. At the time, the populations of both countries greatly resented that the Americans were able to seduce their woman with such ease. Not having much recourse, they lashed out the only way they could, creating silly derogatory terms.
"Oi, thayt bloody seppo had saix wit me wife aynd me two sistuhs!"
by uglyamerican April 09, 2010
 
9.
A clueless bigot that has lost touch with reality. Derived from Sepp Blatter, the cluless bigot that has lost touch with reality
Unfortunately handshakes were not enough for the seppo to convine everyone else he wasn't a complete cunt.
by Ojay82 November 18, 2011
 
10.
What Aussies and Poms call inhabitants of the USA. The majority of them have incredibly low intelligance are are obese.
I don't want to go to the USA, I might get raped by a stinking seppo.
by Poomandow May 27, 2005
 
11.
A person from the Australian state of New South Wales; used as slang derogatory by Victorians and Queenslanders.

Explanation: The three eastern states of Australia are Queensland in the north, Victoria in the south, and New South Wales between them. They are colloquially seen as being Canada, Mexico and the USA respectively. Since seppo is a slang term for American (see above definitions), it becomes a slang term for a New South Welshman.
Victorian: The damn seppos won the 2005 AFL premiership.
by Aspirex January 10, 2006