I usually ask for a definition of "Spirtual" and then sit back and wait for the gum flapping, gibbering and er-ing to subside.

I hate the term 'spiritual. It's what religious people ask after you've said you don't believe in go "But are you a spiritual person?". No I'm fucking not. I'm a normal human being, who feels such intense human emotion sometimes that it makes me blissfully happy. That's all it is- emotion..

Well. You got some pretty half thought out answers to your question in my mind, because for some people spiritual v. religous is a complete outlook or cosmology. Most religions are fertility rituals and genesis stories at their core, but the idea spiritual encompasses all that, and is part of the central definition of agnostic.

Spiritual to begin with fits nicely in the phrase, 'the spirit' of things. So to start with take Christianity's sacrements as a framework to understand, 'the spirit' of things. Then jump through several perspectives such as animism, and the world's major religions to better understand their take on 'the spirit' of things.

Layer all of that with the deeper understanding we can now consider such as images from Hubble, and ecological systems impacting the entire earth as well as other ecosystems. You may want to spend generous time observing the night sky in winter to help hammer home how small we really are in the universe. Don't forget to consider that we can now interpret the human genome along the way as well, and one day we will manipulate it.

Finally(I promise), consider the earth as a single living being hurdled throughout time and space to who the hell knows where with the promise that in about 10 billion years the sun will consume the solar system. What remains?

What remains is that I thought and therefor I was--for me a pretty deeply mystical idea. So, love with all your heart, care until it hurts when appropriate, give back to others what you can, but by all means own your own spirit on your own terms. And that, is why I love being agnostic, with a developed spirit.

I take it as meaning they believe they have a spirit that lives forever, in a heaven, hell, reincarnated body, or floating around in a haunted house or something. They cannot accept the fact that the universe can exist without their consciousness. They will not accept their eventual death.

You can't get any more arrogant than being "spiritual".

I don't get this "spiritual" bit. To me it is just another excuse to believe the unbelievable. Nature 'is' and that is it. We have no idea how 'small' the universe is when compared to something else- but why not study the facts that are already available, instead of making up fairytale nonsense?

Basically they don't just follow one specific organized religion but still superstitious. Might have a few rituals they do. Something like that. Can mean all kinds of gobbledegook, can mean almost nothing. Could be they just aren't ready to admit they are atheist or agnostic or they don't like the other labels... Also, watch out for those people that say they aren't religious but have a relationship with god lol they are especially thick skulled when it comes to religion...

ask them

Cool. If that is all you need to be happy... you are home and pitty the greedy. You cool.

Well, you're halfway there, at least.