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3.
The bully's version of a wife beater: ribbed sleeveless t-shirt.
In the UK, bullies can be spotted from afar, wearing their boy beater tees.
by hammer---;, hytham April 10, 2007
 
1.
another term for 'wife beater', more relevant to the gay community. an a-shirt. a tight, ribbed, white, sleeveless tank-top.
All Shawn ever wears is jeans and a boy beater. He needs to work on his wardrobe.
by bfrd2 February 23, 2006
 
2.
A sleeveless shirt for ladies; a tank top.

As with wifebeater, the name comes from the absence of sleeves, which allows the wearer to beat her boy (or perhaps any boy) unencumbered. This usage was first documented at the Goatwhore merchandise table during their 2012 tour.
After seeing the band's set, she wanted to get their boybeater, but they only had them in large.
by cinquefoil November 24, 2012