Spirit:

An archetype and a functional complex, often personified and experienced as enlivening, analogous to what the archaic mind felt to be an invisible, breath-like “presence.”

Spirit, like God, denotes an object of psychic experience which cannot be proved to exist in the external world and cannot be understood rationally. This is its meaning if we use the word “spirit” in its best sense.[“Spirit and Life,” CW 8, par. 626.]
The archetype of spirit in the shape of a man, hobgoblin, or animal always appears in a situation where insight, understanding, good advice, determination, planning, etc., are needed but cannot be mustered on one’s own resources. The archetype compensates this state of spiritual deficiency by contents designed to fill the gap.[“The Phenomenology of the Spirit in Fairytales,” CW 9i, par. 398.]

Jung was careful to distinguish between spirit as a psychological concept and its traditional use in religion.
From the psychological point of view, the phenomenon of spirit, like every autonomous complex, appears as an intention of the unconscious superior to, or at least on a par with, intentions of the ego. If we are to do justice to the essence of the thing we call spirit, we should really speak of a “higher” consciousness rather than of the unconscious.[“Spirit and Life,” CW 8, par. 643.]

The common modern idea of spirit ill accords with the Christian view, which regards it as the summum bonum, as God himself. To be sure, there is also the idea of an evil spirit. But the modern idea cannot be equated with that either, since for us spirit is not necessarily evil; we would have to call it morally indifferent or neutral.[“The Phenomenology of the Spirit in Fairytales,” CW 9i, par. 394.]

http://www.nyaap.org/jung-lexicon/s