[From Latin spiritus: the animating principle of humans or of supposed non-physical beings.]
(metaphysics) The belief that there exist purely spiritual entities that do not have bodies or other physical manifestations, or that there exists a spiritual world or realm above and beyond the physical world.
(epistemology) Another term for mysticism.
(ethics) The view that spiritual concerns are more important than this-worldly concerns (a kind of idealism or asceticism that is opposed to secularism).