The word "spiritual" refers to the part of the human being which is not material. There is only one aspect of the human being which is not material: his mind. The mind, or consciousness or spirit of man is not an entity on its own, an entity that can live by itself without a body and without a physical brain that produces it. The spirit of man is not a ghost trapped somwehere in the body, waiting to be finally free when the body dies!
Anything that pertains to our consciousness, our ability to perceive reality through the senses and transform our percepts into CONCEPTS is spiritual, non material. Our thoughts. ideas, concepts, knowledge, emotions, sentiments, feelings, sensation, opinions, hypotheses, etcetera are examples of spiritual PRODUCTS of our consciousness.
Since we are not omniscient and infallible, what we perceive of reality and what we abstract from our perceptions can be right and wrong, can be rational and irrational, can be real and imaginary, can be true or false. If we choose to practice the VIRTUE of rationality, we have a chance at knowing reality. If we don't, we are like people who travel without a map.
Rationality is the highest spiritual human virtue. Without it we cannot distinguish the real from the unreal, the true from the false, the just from the unjust and the moral from the immoral.
Religion is just a mystic form of philosophy that takes us to believe in supernatural entities and events that are not part of reality at all.