The Foster's Lager reference article from the English Wikipedia on 24-Jul-2004
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Foster's Lager

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Foster's Lager is an internationally-distributed, Australian brand of beer produced by Foster's Group.

Whilst popular in many countries, where it is often brewed under license, and popularised by advertising making use of stereotypes of Australians as unsophisticated bush-dwellers, Fosters Lager is highly unpopular in its home country - mainly because it is popularised overseas by advertising making use of stereotypes of Australians as unsophisticated bush-dwellers. Victoria Bitter, brewed by Carlton & United Breweries, a subsidiary of Foster's Group, is in Australia almost universally regarded as a superior low-cost "basic" beer.

It might be wothwhile noting at this point that the word "piss" in Australia has a couple of shadings of meaning when used colloqually. It may mean beer in general, or cheap beer, or beer when viewed as a means to become "pissed". 'Pissed' means 'drunk'. It does not mean 'angry', although 'pissed off' does. Hence the american sitcom oh my gawd I was so pissed! requires a little mental translation. However, referring to a particular brand of beer as 'piss' is pejorative: hence "Fosters? That stuff is piss!".

The Fosters brand is also used in Australia on several other beers, notably Fosters Light Ice, a low-alcohol lager.