architrave

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

• noun The lowermost part of an entablature in classical architecture that rests directly on top of a column.
• noun The molding around a door or window.

from The Century Dictionary.

• noun In architecture: The lower division of an entablature; that member which rests immediately on the column and supports those portions of the structure which are above it. See cut under entablature.
• noun The ornamental molding running round the extrados of an arch. Also called archivolt.
• noun Sometimes, less properly, the molded enrichments on the faces of the jambs and lintel of a door, window, or other opening. Also called antepagment.
• noun In fortification, the master-beam, or chief supporter, in any part of a subterranean fortification.

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

• noun The lower division of an entablature, or that part which rests immediately on the column, esp. in classical architecture. See column.
• noun The group of moldings, or other architectural member, above and on both sides of a door or other opening, especially if square in form.

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

• noun architecture The lowest part of an entablature; rests on the capitals of the columns
• noun architecture The mouldings (or other elements) framing a door, window or other rectangular opening

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

• noun the molding around a door or window
• noun the lowest part of an entablature; rests immediately on the capitals of the columns