door

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

• noun A movable structure used to close off an entrance, typically consisting of a panel that swings on hinges or that slides or rotates.
• noun A similar part on a piece of furniture or a vehicle.
• noun A doorway.
• noun The room or building to which a door belongs.
• noun A means of approach or access.
• transitive verb Slang To strike (a passing bicyclist, for example) by suddenly opening a vehicular door.
• transitive verb To serve as a doorman or doorwoman of (a nightclub, for example).
• idiom (at (someone's) door) As a charge holding someone responsible.
• idiom (close/shut) To refuse to allow for the possibility of.
• idiom (leave the door open) To allow for the possibility of.
• idiom (show (someone) the door) To eject (someone) from the premises.
• idiom (show (someone) the door) To terminate the employment of; fire.

from The Century Dictionary.

• noun A movable barrier of wood, metal, stone, or other material, consisting sometimes of one piece, but generally of several pieces framed together, commonly placed on hinges, for closing a passage into a building, room, or other inclosure.
• noun An opening for passage into or out of a building or any apartment of it, or any inclosure; a doorway.
• noun Hence—3. An exterior or public entrance-way, or the house or apartment to which it leads.
• noun Avenue; passage; means of approach or access, or of exit: commonly in figurative uses: as, the door of reconciliation; a door of escape.
• noun Near to; bordering on; very nearly.
• noun Hence, figuratively, quite gone; no more to be found; lost; irrelevant.
• noun Figuratively, to ruin one.

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

• noun An opening in the wall of a house or of an apartment, by which to go in and out; an entrance way.
• noun The frame or barrier of boards, or other material, usually turning on hinges, by which an entrance way into a house or apartment is closed and opened.
• noun Passage; means of approach or access.
• noun An entrance way, but taken in the sense of the house or apartment to which it leads.
• noun etc. (Arch.) See under Blank, Blind, etc.
• noun within the house.
• noun near to; bordering on.
• noun out of the house; in open air; abroad; away; lost.
• noun to charge one with a fault; to blame for.
• noun to be imputable or chargeable to.

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

• noun A portal of entry into a building or room, consisting of a rigid plane movable on a hinge. Doors are frequently made of wood or metal. May have a handle to help open and close, a latch to hold the door closed, and a lock that ensures the door cannot be opened without the key.
• noun Any flap, etc. that opens like a door.
• noun A non-physical entry into the next world, a particular feeling, a company, etc.
• noun computing, dated A software mechanism by which a user can interact with a program running remotely on a bulletin board system.
• verb transitive, cycling To cause a collision by opening the door of a vehicle in front of an oncoming cyclist or pedestrian.

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

• noun a swinging or sliding barrier that will close the entrance to a room or building or vehicle
• noun a structure where people live or work (usually ordered along a street or road)
• noun a room that is entered via a door
• noun anything providing a means of access (or escape)
• noun the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close