A
recovering alcoholic, especially someone in
Alcoholics Anonymous, or anyone in a similar
12-step program.
This code phrase, like the mantra "One Day At A Time" and the equilateral triangle inscribed in a circle, is used to discreetly identify others in the same group. Since other people (such as myself) recognize these signs, it's only a discreet way of asking -- not a particularly secret way.
Bill W. is the founder of AA.