A truss is a framework that supports something, like a roof or a bridge. A steel beam that holds up a bridge is called a truss. Another kind of truss is a similar structure that's designed to support a roof.
A truss refers to part of the design of a bridge, overpass, or building; or a medical device that keeps a hernia from bulging. Either way, a truss offers support. You can also use truss as a verb meaning "tie up." Many cooks are familiar with a recipe's instruction to truss a goose, for example, tying its wings and legs together before cooking it. A truss was originally "a collection of things bound together," with the Vulgar Latin root torciare, "to twist."