boiler room

a room in a building, ship, etc., that houses one or more steam boilers.

Slang.

a place where illicit brokers engage in high-pressure selling, over the telephone, of securities of a highly speculative nature or of dubious value.
any room or business where salespeople, bill collectors, solicitors for charitable donations, etc., conduct an intensive telephone campaign, especially in a fast-talking or intimidating manner.

OTHER WORDS FROM boiler room

boil·er-room, adjective

In some cases the curing-room is located over the boiler-room and hence becomes very hot.

The Book of Cheese |Charles Thom and Walter Warner Fisk
Bewildered, but unhurt, he crawled to the boiler-room, shaking the coal from his back and shoulders.

The Best Short Stories of 1917 |Various
It is sucked up from the machines and carried in large tubes to the boiler-room and there is mechanically supplied to the fires.

Handwork in Wood |William Noyes
The boiler-room's bad enough, I grant ye that, but it's a darn sight better than goin' to jail.

By Right of Conquest |Arthur Hornblow

Neville had heard Larry's cry and rushed to the boiler-room.

The Best Short Stories of 1917 |Various

boiler room

any room in a building (often in the basement) that contains a boiler for central heating, etc

the part of a steam ship that houses the boilers and furnaces

the room or department in which the real work of an organization goes on unseen

(chiefly US) an office used by a team of telephone salespeople, esp of stocks and shares, operating under high pressure

a fraudulent scheme in which investors are encouraged to buy non-existent, worthless, or over-priced shares
(as modifier)a boiler-room scam