A
window open in the
dead of winter, as used by tenants of apartments with building-controlled heating (typically steam radiators), which presumably doubles as a basement
blast-furnace and would otherwise boil the occupants alive. So-named for its prevalence in the NYC borough and similar metropolitan areas with many pre-war buildings.
"That open
window ain't a '
waste of energy,' it's the Brooklyn thermostat, and I swear d'ya it's the only
thing keepin' us all from becomin' kebabs!"