Final answer:
A supporting member that is self-supported at only one end and projects into space is known as a cantilever.
Step-by-step explanation:
A cantilever is a rigid structural element that extends horizontally and is unsupported at one end. Typically it extends from a flat vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cantilever can be formed as a beam, plate, truss, or slab. A supporting member that projects into space and is self-supported at only one end is called a cantilever.
Unlike a beam, which is supported at both ends, or a column, which is typically vertical and carries loads from above to the foundation, a cantilever extends outward and is anchored on only one end. Cantilever construction allows for overhanging structures without external bracing. Trusses, on the other hand, are composed of interconnected elements forming triangular units, typically used to support other structures, and don't match the definition of being supported at only one end.