girder

American Heritage® Dictionary of the English Language, Fourth Edition

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

Century Dictionary and Cyclopedia

1. n. 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. Wooden girders, when in two or more pieces, take the form of built-up beams, arched beams, or compound beams. When composed of upper and lower horizontal members, united by vertical and diagonal pieces, the girder is called a lattice-girder. When reinforced by iron rods a wooden beam may form a trussed girder. Iron girders are simple or compound, and are made of cast-iron or wrought-iron, or both combined. The most simple form is the common rolled or cast I- or T-beam. Compound beams are composed of plate- and angle-irons built together in various forms, the most simple having a plate-iron web united to upper and lower plate-iron members by means of angle-irons. More complicated forms include girders with two webs (the box-girder) or with three or more webs, or with groups of rolled beams united. Iron girders also appear in many latticed forms, and are largely used in bridge-building. (See bridge, girder-bridge.) A very notable and extensive use of girders is in the structure of elevated railroads. Also called girding-beam.
2. n. one who girds or gibes; a satirist.

Wiktionary

1. n. A beam of steel, wood, or reinforced concrete, used as a main horizontal support in a building or structure

GNU Webster's 1913

1. n. One who girds; a satirist.
2. n. One who, or that which, girds.
3. n. (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.

WordNet 3.0

1. n. a beam made usually of steel; a main support in a structure