anteroom

noun

Etymology: From ante- + room, as a calque of French antichambre or its model Italian anticamera.

1. A room before, or forming an entrance to, another; a waiting room.

   “[T]his was one of the anterooms off the main throneroom in which the king was accustomed to hold court with his entire retinue.”

   “Several antique games, such as a skiddles table, occupy an upstairs anteroom.”