castor fiber(n = noun.animal) old world beaver - a European variety of beaver;
is a kind of beaver

acrylic fiber, animal fiber, bast fiber, castor, castor and pollux, castor bean, castor bean plant, castor canadensis, castor oil, castor sugar, cotton fiber, fiber, fiber bundle, fiber optic cable, fiber optics, genus castor, glass fiber, man-made fiber, medullated nerve fiber, motor nerve fiber, muscle fiber, myelinated nerve fiber, natural fiber, nerve fiber, optical fiber, plant fiber, polyester fiber, purkinje fiber, staple fiber, striated muscle fiber, synthetic fiber, tampico fiber, vulcanized fiber