Dating from at least the 1940s, and used as a slogan used during the UK miners' strike, A.C.A.B. is an abbreviation often integrated into prison tattoos in the United Kingdom, it is most commonly rendered with one letter between the knuckle and first joint of each finger, sometimes as symbolic small dots with or without the accompanying letters on each knuckles.
"A.C.A.B." stands for "All Cops Are Bastards" but can also stand for "All Coppers Are Bastards" (or, depending on who is asking, "Always Carry A Bible").
The British Oi! punk band, the 4-Skins, popularized the acronym A.C.A.B. in their 1970s song of the same name. It is currently in common usage as a phrase and tattoo amongst some ultras groups in Europe, particularly in Eastern Europe where most groups are more akin to hooligans than ultras.

On the 7th January 2011, three Ajax football fans were fined for wearing t-shirts with the numbers 1312 printed on them. 1312 stands for ACAB.