CHAV - working class boor. From British slang. "“This club used to be nice, but now it's full of chavs."
I find this borrowing of the British term a bit sad, since it necessarily involves some semantic shift or drift. It's not so much that I'm against linguistic change and borrowing, but chav describes a very particular social phenomenon, which is generally not found in the same way in the US--with the notable possible exception of Britney Spears. The word becomes less useful if it just refers generally to 'working class boors'.
Britain, on the other hand, does not have exact equivalents of the American phenomena rednecks, trailer trash or wiggas, although there are overlaps between the latter two and chavhood.
A key difference between the US and UK social stereotypes is their relation to race and class issues. The US categories all implicitly or explicitly reference race--rednecks are whites who stereotypically have racist attitudes, trailer trash is a subcategory of white trash, and wiggas are (typically/originally upper middle class) whites who emulate 'urban black' styles. While chavs are generally white, and while their style and slang often echoes an 'urban' Black American aesthetic (e.g. bling), the relationship is less direct than for wiggas. Football (AmE: soccer) also plays a heavy role in chav style, whether in emulation of favo(u)rite players (or their wives), or in the display of football-nationalistic symbols (e.g. England team wear). Click here for a football-themed post on World Cup words.
Chavhood is also associated with Gypsydom, although more through shared stereotypes than actual lineage. The word itself is thought to be Romany in origin (see Michael Quinion's excellent site), and pikey, an offensive word for Gypsies (or Travel(l)ers, a preferred term in Britain), is often used as a synonym for chav.