The term Spirit is one of several terms (others include God, The Fabric of Consciousness, energy, matter and so on), which can be used to refer either to consciousness as a whole, or to some aspect of it.
The word "spirit" is typically used when we are referring to consciousness "outside" the Physical Unit. A spirit, or the spirit, is a Monadic Consciousness that is not currently incarnated in a physical unit.
Sharp, Michael (BOLVI). The Book of Light - The Nature of God, the Structure of Consciousness, and the Universe Within You. Volume One - Air. Lightning Path Press.