BOGOF
UK abbreviation for uk/bɒɡˈɒf/ us/bɑːɡˈɑːf/
买一送一（商店的一种促销方法，顾客购买一件商品，就能免费获得另一件同样的商品，buy one get one free 的缩写）
buy one get one free: an offer used in shops, in which if you buy one thing, you get another of the same thing for no extra cost