A secluded or unobtrusive
building or
apartment considered safe for
use by
secret agents as a base of operations, as a
refuge,
hideaway or for a
personal
meeting. Archetypically, out in the
middle of nowhere, with
generator,
cistern, and the like, it can sometimes simply be a city apartment that keeps a
very low profile.
"Oh, the Smiths? You hardly see or hear them..."
Alternatively, a legendary night club/discotheque in Milwaukee, Wisconsin, behind a door marked "Universal Imports", and otherwise unmarked and NOT in the phone book...hmmmm....