Bob, here is this definition from the Urban Dictionary
Friend of Bill W.
A member of Alcoholics Anonymous (AA), and therefore (usually) a recovering alcoholic. Derived from the name of Bill Wilson (Bill W.), one of the founding members of AA.
If you are at an airport and have a temptation to head to one of the bars, instead have "Bill W." paged, as code for your need for someone from the program come have a "meeting" with you.