n. The denial of the existence in man of an immaterial substance, which alone is conscious, distinct and separable from the body.n. The metaphysical doctrine that matter is the only substance, and that matter and its motions constitute the universe. See idealism, 1.n. The doctrine that all phenomena are to be accounted for by the fortuitous concourse of atoms, in connection with certain laws or tendencies toward laws, in nature; Epicureanism.n. Any opinion or tendency that is based upon purely material interests; hence, any low view of life; devotion to material things or interests; neglect of spiritual for physical needs and considerations.