a passage, hall, or antechamber between the outer door and the interior parts of a house or building.

Railroads . an enclosed space at the end of a passenger car, serving as a sheltered entrance to the car from another car or from outside the train.

Anatomy, Zoology . any of various cavities or hollows regarded as forming an approach or entrance to another cavity or space, as that of the internal ear.

to provide with a vestibule.

noun

antechamber , anteroom , doorway , entrance , entrance hall , entry , entryway , foyer , gateway , hall , hallway , lobby , narthex , porch , portal , portico , cavity , channel , corridor , passage