1rare The quality or condition of being energetic.
historical The doctrine or theory that changes in energy form the basis of all physical phenomena, and that energy is the fundamental constituent of the universe.
This theory, advocated as an alternative to atomic theory, is chiefly associated with the German physical chemist Wilhelm Ostwald (1853–1932). Even after abandoning energeticism as a scientific hypothesis, Ostwald continued to advocate it as a general metaphysical theory.
Late 19th century; earliest use found in New York Recorder. From energetic + -ism.