All the time I was a witness, the term "spiritual" was used as an adjective. Overused, I might add, to the extent that it totally lost its meaning. Ask any two witnesses and you will not get the same definition. I've carried that perplexity about the word for most of my adult life.
I am a religious person, not in the sence that I crave gathering together, or ritual or needing a reference group to define me. I have a world view that is determined on my conviction that is a product of what I have come to believe is a sequence of events, patterns if you will, that repeat themselves and as a function of cause and effect have affected the would of humanity for its ever-advancement. I find this for me to be true. It is a "religious" belief. I would most likely not be a "spiritual" person if the social and intellectual aspects of my religion did not regularly reinforce the concept of moral and ethical integrety. I would be much more hedonistic and selfish if I did not have the religious convictions that I have.
What is "spiritual"? Personally, it is the sum total of the moral and ethical decisions we make and the resulting actions. Faith is the conviction that there is a connection between those mindsets and a source that causes humans to have those convictions. Religion is the sociatal construct that reiforces the manifestation of moral and ethical character. When it ceases to perform the function of education and pacification, it is fit for the fire. As Jesus said, "the tree that ceases to bear fruit, is fit for the fire". When a religion ceases to be a positive force for humanity, it needs to be re-newed. Simple.