[this section must be entirely rewritten in order to integrate freedom - the uncaused and non-random creation out of what we can only call as "nothing" - and the role of stilness]
Spirituality may mean many things, in general it means some strange, almost unachievable thing. Something to be attained in the end of an arduous life, as a kind of prize, etc.
For some it is like to be a hero: realizing almost the unthinkable, being an unconditional lover in a world full of bad guys who want to do evil and so we have to remain wise and pure, etc. (some Catholics are like this)
For some it is being beautiful, doing beautiful things, recognizing beauty, etc (the artist).
For some it is to be knowledgeable, impartial, critical even skeptical, not to fall into the easy answers that may comfort our hopes but are nothing more than illusions to keep the weak and coward satisfied (the scientist and some kinds of philosophers).
For some it is to dissolve, "wherever you are God is not, whenever you are not God is" (Osho, Zen Buddhism, etc)
For some is the dharma, pursuing detachment and Nirvana and at the some time helping others, etc (Tibetan Buddhism, etc).
For some it is being very humble and meek (protestant are more in that line)
etc
There are many, many ways of interpreting what it means to be "spiritual" perhaps each person on the planet has its own understanding of what that means. So here is my two cents, for me, being spiritual is merely being honest and open to the world, not deny anything we are able to see (or experience or think), not to affirm anything that we are not sure of, and also not to have secrets. In sum, for me being spiritual is just being clear, or at least being clear in the measure that we can achieve it. This has some similarities to the scientific approach because it emphasizes the avoidance of lies and other kinds of comforting defenses. The difference from the scientific approach is that I think we should be open to everything we experience. If science is just an attempt to describe the physical aspect of the world then it should consider itself a very limited field of research within human experience. If, on the other hand, science is the attempt to understand the "universe" (understood as everything there is) then it must necessarily attempt to encompass everything there is including my will, my passions, my love. There are no consensual explanations for these kinds of realities today, so science should just say: «this is something we must investigate better, we are open to ideas, for the moment we simply don't know, what is your suggestion?» This investigation attitude would help immensely in not breaking the world of spiritual experience from the world of physical experiment. In fact they are the same world. Scientists studying super-conductivity have emotions like two lovers making love, as much spirituality as a priest in Sunday dress. It is only one world. The division is in our heads, when we refuse some fields of human experience as unapproachable or we just dismiss the any kind of spiritual experience as the result of emotional imbalances or mythomania we are indeed reinforcing these divisions. The fact that we are not interested in some topics of research is in itself quite benign, but our despise for them (either from the spiritual or the physical part) creates tremendous tension in society, of the kind "men against themselves", which is a pity, so much energy wasted in destroying one another that could be used for growing together. There is so much to see, such a long way to walk, so much to experience, every time we waste our time against each other we are indeed losing the opportunity to be on our way.
To be clear... why do I want to be clear? Because I want to transparently live the mystery...