antechamber

nown

Definition:

a small outer room that leads to another room and that is often used as a waiting room

Example:

Please wait in the antechamber for the baron’s servant to call you in.

Personal Commentary:

This one’s a gimmie, it’s common for describing any waiting room, or room that funnels people before a large chamber (like in a keep, palace, or dungeon). It can be used in dialogue or narration.