Green’s Dictionary of Slang

A.B. n.

[abbr.]

1. [1980s+] (N.Z.) the menstrual period [abbr. Annie Brown, on the model of menstruation = a ‘visiting’ woman].

2. [1980s] (US) fools as a group, lit. Asshole Brigade [asshole n. (3)].

3. [1970s+] (US prison) Aryan Brotherhood, the white supremacist organization that unites many white convicts during (and after) their time in jail.

4. attrib. use of sense 3.

5. [1990s+] (Aus. prison) Aryan Breed; the Aus. version of sense 3.