I guess I can be an atheist and also be spiritual. However, I can't seem to figure out how. I think Buddhist claim to be spiritual, and spirituality means something to them. I see religious people become filled with emotion during singing and worship so I guess they call that spiritual. I guess worshipers speak in tongues are experiencing some kind of spirituality. maybe a sense of heightened awareness is spirituality. I dunno.

Spiritualism is much like religion in the respect that it has different meanings to everyone. It may be linked to karma, souls, and of course the "spirit of the gaps".

Spiritualism is frankly bollocks that I wasted a couple of years of my life on.
The cult was originally founded by seamstress sisters Leah, Kate and Maggie Fox, who started it as a scam in 1848 to sell cotton underwear to "the faithful" who they explained needed it in order to be in tune with the "dear departed" ( a trick that was ripped off wholesale by the Mormons a couple of years later)
The lie got way out of hand until the "religion" fractured in to two major sects "The spirtualist church" and the Christian Spiritualist."
Each faction developed a major denomination
Greater World Christian Spiritualism ( The Greater World Spiritualist League and The Greater World Christian Spiritualist Association) who follow the teachings of their prophet Zodiac, who relayed his holy text from beyond the grave to a string of mediums starting with Winifred Moyes
and
The National Spirtualist Union who follow the seven Principles of eternal progress and do not limit themselves to being Christian but embrace all faiths and oddly, those of no faith but who believe in eternal progress.
THe NSU are by far the richer organization gathering most of their wealth from a string of "Colleges" teaching everything from mediumship to aromatherapy, tantric magic and crystal healing, selling endless books and holding weekly services with an entrance fee, and special events called transfiguration services that charge anything up to £50 a ticket (or did when I was there) depending on how famous the Medium is and who the "Philosopher" is philosophers in the NSU are those relaying the sermons on how to be a good spirtualist.

Ironically very few denominations of wither branch use seances or table tapping the methods used by the fox sisters, but instead cold read audiences, some put on quite a good show, in the UK in late eighties a (sadly now deceased) Rosicutionist Medium named Mick Foley commanded big audiences large fees and was one of the funniest men I have ever seen, you did not leave his meetings enlightened but you were happier then when you went in.

My personal favourite was a woman going by the name of Little Nell, who was in her 90's and had been a medium for over seventy years, she famously told one patron
"I have your mother here"
The woman cried
"My mother is not dead, I just left her at home"
"Oh," Said Nell then added. "Still that was over an hour ago wasn't it"
Sending the poor congregant screaming in to the night.

It is the name that people give to emotions which they get, when they can not find a rational cause for them.

It is the emotional equivalent therefore of, the god of the gaps. I can't explain this emotion, therefore it must be supernatural in origin.

Perhaps you are asking about spirituality, which IS ill-defined. SpiritualISM is belief that the spirits of the dead communicate with the living. SpritualITY is whatever people claim it is, basically.

There is no single, widely agreed upon definition of spirituality.[2][3][note 1] Surveys of the definition of the term, as used in scholarly research, show a broad range of definitions with limited overlap.[1] A survey of reviews by McCarroll each dealing with the topic of spirituality gave twenty-seven explicit definitions, among which "there was little agreement."[1] This impedes the systematic study of spirituality and the capacity to communicate findings meaningfully. Furthermore, many of spirituality's core features are not unique to spirituality; for example self-transcendence, asceticism and the recognition of one's connection to all were regarded by the atheist Arthur Schopenhauer as key to ethical life.[18][better source needed]