Not to be too academic about answering the question : What is spirituality, but........
Here are my two cents. If not convincing I'll refund your coins!
I think primitive man had primitive ideas, naturally, and tried his best to figure out what was happening and why.
One of the things primitive man observed was the difference between something living and something dead. (I mean, besides the smell).
A dead person stopped breathing! What was going in and out of a living person that went out and didn't come back from a dead person? Hmmmm, let's see now......I know! Breath. Air. Or, simply SPIRIT.
From that concept all sorts of fanciful guesses, stories, myths and crackpot reasonings became attached and embellished.
From that simple observation, I believe, the whole notion of invisible life force or ghosts or demons, or gods evolved. A primitive person must have been fascinated, puzzled and wowed by the fact you could FEEL the air but not see it. (That was before the city of Los Angeles).
We get the idea of a Soul, mainly from such imaginings about the breath of a person.
Fast forward. Modern times.
People have been disgusted with formal religion for quite some time because of the wacky and hurtful things that come out of it. But, people are also very attached to the warm and fuzzy feeling of mental comfort that comes from having the rabbit's foot in the sky. So, they throw out the "formal" organized body of rules and rule-makers and cling to the barebones concept beneath it all. Which is what? Why the hidden part, of course!
Mysticism thrives on hidden concepts and undefinable ideas and unprovable beliefs.
Today a SPIRITUAL person is one who superstitiously insists on the power of the invisible to alter their life for good or ill. It is a fantasy and magic-thinking, naturally, but it has an emotional core to it and we all crave strong emotional feelings.
Mostly we find people clinging to any old mystical notion that satisfies their "inner child" and brings them out of day to day life (which we all know is too REAL and a genuine drudge!).
Some examples of mystical or Spiritual thinking are evident in catch phrases you hear people mention all the time. It imports MEANING and Destiny into ordinary events.
1.Everything happens for a reason; nothing happens by chance.
2.We all have a soul mate out there; we just have to be open to finding them.
3.God has a plan for my life!
4.There are no coincidences!
5.Ohhhh, that's spooky; I wonder what that "MEANS"?
6. I can't believe you called! I was just thinking about you!
We have all heard these things. Superstitious people simply insist that somebody or something is in charge of the Universe and plots it out like an Agatha Christie novel.
To me that is what it means to be SPIRITUAL. It is refusing to deal with reality by means of evidence, facts, knowledge or autonomy and it leads to vagueness, naivete and actions based on nothing more than coincidence or magic thinking.
But, heck--don't listen to me. What do I know?