Monolithic architecture is a style of construction in which a building is carved, cast or excavated from a single piece of material. The most basic form of monolithic architecture is the monolith, such as the monolithic churches of Lalibela or the Pancha Rathas in India.
Buildings with a structural material which is poured into place, most commonly concrete, can also be described as monolithic. Extreme examples are monolithic domes, where the material is sprayed inside of a form to produce the solid structure. http://en.wikipedia.org/wiki/Monolithic_architecture