Look up antechamber in Wiktionary, the free dictionary.
An antechamber (also known as an anteroom or ante-room) is a smaller room or vestibule serving as an entryway into a larger one. The word is formed of the Latinante camera, meaning "room before".
In some cases, an antechamber provides a space for a host to prepare or conduct private business away from a larger party or congregation. In a theme park, an antechamber may be used to tell guests about a ride before they experience it.