Fibrous plaster is the common name in the Great Britain for the type of plasterwork that is more commonly referred to as plaster moldings or occasionally pre-cast plaster in North America. However, fibrous plastering I would maintain is a more accurate description as this technique in plaster working is used not only for the extrusion of molding profiles but also for ornament and panels among other casting applications. As the name implies, plasterwork of this variety is reinforced with fibers. Traditionally, these are derived from grasses and plants such as hemp, jute, sisal and even coconut.
Additionally, wood wool (aka excelsior, typically that of Aspen and Poplar) is in common use for many plaster applications. All of these could be thought of as serving a similar function that rebar provides concrete, that of reinforcing the plaster and increasing its tensile strength.