vestibule

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small entrance hall or passage between the outer door and the interior of a house or building.
• noun An enclosed area at the end of a passenger car on a railroad train.
• noun Anatomy A body cavity, chamber, or channel that leads to or is an entrance to another body cavity.

from The Century Dictionary.

• noun In Bryozoa of the suborder Cryptostomata, a tubular shaft which lies above and leads to the mouth of the zoœcium. This vestibule or vestibular shaft may be crossed by diaphragms or hemisepta and is surrounded by vesicular tissue or a solid calcareous deposit.
• noun In car-building, a car-platform inclosed above and on two sides and connected by a bellows-like extension with the similarly inclosed platform of the next car. Each extension carries an iron doorframe called a face-plate. When two cars are coupled together the opposing face-plates are pressed together by springs, which at the same time allow them to slip over one another with the motion of the cars. The permanent structure of the vestibule includes doors on each side, at the steps, and hinged platforms to cover the steps when the doors are closed.
• noun A passage, hall, or antechamber next the outer door of a house, from which doors open into the various inner rooms; a porch; a lobby; a hall; a narthex. See cuts under opisthodomus, porch, and pronaos.
• noun In anatomy: A part of the labyrinth of the ear, the common or central cavity, between the semicircular canals and the cochlea, communicating permanently with the former, and temporarily or permanently with the latter, from the proper membranous cavity of which it is generally shut off subsequently, opening into the tympanum or middle ear by the fenestra ovalis, which, however, is closed in life by a membrane. See cuts under car and temporal.
• noun A triangular space between the nymphæ or labia minora of the human female and some anthropoid apes, containing the orifice of the urethra, or meatus urinarius. More fully called vestibule of the vulva and vestibulum vaginæ.
• noun A part of the left ventricular cavity of the heart, adjoining the root of the aorta.
• noun In zoology: A depression of the body-wall of sundry infusorians, as Paramecium and Noctiluca, leading to the oral and sometimes also to the anal aperture, and thus connected, by means of an esophageal canal, with the endosarc. See Vorticella, Noctiluca, and cut under Paramecium.
• noun In polyzoans, an outer chamber of a cell of the polyzoary, which opens on the surface, and into which, in some forms, the pharynx and anus both open.
• To provide with a vestibule.

from the GNU version of the Collaborative International Dictionary of English.

• noun The porch or entrance into a house; a hall or antechamber next the entrance; a lobby; a porch; a hall.
• noun (Anat.) See under Ear.
• noun (Anat.) a triangular space between the nymphæ, in which the orifice of the urethra is situated.
• noun (Railroads) a train of passenger cars having the space between the end doors of adjacent cars inclosed, so as to admit of leaving the doors open to provide for intercommunication between all the cars.
• transitive verb To furnish with a vestibule or vestibules.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun architecture A passage, hall or room, such as a lobby, between the outer door and the interior of a building.
• noun rail transport An enclosed entrance at the end of a railway passenger car.
• noun medicine, anatomy, by extension Any of a number of body cavities, serving as or resembling an entrance to another bodily space.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various bodily cavities leading to another cavity (as of the ear or vagina)
• noun a large entrance or reception room or area