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1.
A Sydney Surf Tribe or Gang famous for their involvement in the 2005 Cronulla Riots. Although the tribe themselves claimed that they did not iniate the riots, they were a major part of them and caused many injuries. They are also preserved in the 2007 Film, Bra Boys, and are marked by their significant and recognizable tattoos.
The Bra boys come from maroubra and are a gang or tribe
by Snafflepops March 30, 2009
 
2.
A good time had by a group of 3 or more people at some form of social gathering.

Originally from the name of a notoriously fraternal surf gang from Sydney's southern beach area.
I thought the party would be shit but it was a bra boys.

Do you wanna come over and have a bra boys?
by vinvanvoosch June 23, 2010