Under the Radar:
A provider who maintains a very low profile, rarely advertises, usually prefers not to be reviewed, and rarely participates on discussion boards.  Usually only sees long-term clients ('regulars'), and only takes referrals for new clients.

See link below for additional definitions.

In checking I had yet to add that acronym to the glossary. (Any other additions needed feel free to PM me)

 FR.

Here's one I've been seeing lately and can't figure out.... BCD?

BCD = Behind Closed Doors.