girder

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

• noun A beam, as of steel, wood, or reinforced concrete, used as a main horizontal support in a building or bridge.

from The Century Dictionary.

• noun one who girds or gibes; a satirist.
• noun One who or that which girds, binds, or encircles. Specifically A main beam of either wood or iron, resting with each end upon a wall or pier, used to support a superstructure or a superincumbent weight, as a floor, the upper wall of a house, the roadway of a bridge, or the like.

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

• noun One who girds; a satirist.
• noun One who, or that which, girds.
• noun (Arch. & Engin.) A main beam; a stright, horizontal beam to span an opening or carry weight, such as ends of floor beams, etc.; hence, a framed or built-up member discharging the same office, technically called a compound girder. See Illusts. of Frame, and Doubleframed floor, under Double.
• noun etc. See under Bowstring, Box, etc.
• noun See under Bridge.
• noun a girder consisting of longitudinal bars united by diagonal crossing bars.
• noun a girder consisting of horizontal upper and lower bars connected by a series of diagonal bars sloping alternately in opposite directions so as to divide the space between the bars into a series of triangles.
• noun a girder consisting of two parallel wooden beams, between which is an iron plate, the whole clamped together by iron bolts.

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

• noun A beam of steel, wood, or reinforced concrete, used as a main horizontal support in a building or structure

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

• noun a beam made usually of steel; a main support in a structure