I'll take a stab at defining "spiritual", at least the way I understand it. I think of it as a "recipe" or pattern for something in reality. A little bit related to Plato's "forms" but not exactly. "Recipe" is a better way to think of it. In traditional cosmology, they used the word "heaven" to refer to "patterns" or "recipes" or "seeds". A seed is another good way to think of it. A seed is tiny and contains the recipe or pattern for the thing it will grow into.
In traditional cosmology, if you have "heaven", you also have "earth", which means potential, or chaos, or unorganized matter. Or if we want to keep the "recipe" metaphor, this would be the "ingredients".
So we have a recipe (the spiritual pattern) and we have the ingredients (matter), and we combine the ingredients using the recipe (we are co-creating with God) a new substance. We transform the ingredients into a new object (bread, in our case) which gets a new name, because it is related to the ingredients, but is now unified by being transformed as we co-create a new object with God. Each new object is slightly different (a "particular"), but it's following a pattern or recipe, so we still recognize it as a particular example of a pattern we call "bread".
This same pattern of "heaven" and "earth" applies to seeds and soil, or an idea and a project, or a film script and a film. This is what is meant when traditional cultures and books speak of "heaven" and "earth".
So to live a "spiritual" life would mean to seek out and learn to identify "patterns" and to manifest them bodily by acting them out or by transforming matter to make a new object. Which is what all humans do all day every day, but our materialist minds have been blinded to how essential and common this is to the human experience, because we get caught up trying to "scientifically" understand what "heaven" is, but heaven is an ontological category, not a scientific place.