This word is generally used in everyday speech by persons who cannot tell you in positive terms what they mean by it. If you ask them for a synonym, they cannot give it to you. They have only some vague ideal of what they are referring to.
Philosophically, the only precise meaning of the words "spirit" and "spiritual" is negative, not positive. What is spiritual is immaterial. God is spiritual, the angels are spirits, and the human intellect -- the intellect, not the soul -- is a spiritual power, which is to say it is immaterial. (See Man and Soul.)