- vestibule⇄noun 1a. a passage, hall, or chamber immediately between the outer door and the inside of a building; antechamber, entrance hall, or lobby.
b. an enclosed or covered area in front of the main entrance of ancient Greek andRoman buildings; forecourt - vestibule⇄v.t. 1. to replace the open platforms, once universal on railroad trains, by vestibules.
2. to couple (railroad cars). - vestibule⇄vestibule, noun, verb, -buled,-buling.