Words at Work
Georges Bataille, the French philosopher, novelist, and pornographer, used to talk about the "job" of a word, not what it means or what it refers to but what it is used for. Like many other theological words, spirituality doesn't have very much to offer on a conceptual level--nobody is very interested in specifying what it denotes--but many people obviously find it useful.
Sometimes people appeal to spirituality as a way of complaining about the narrowness of the scientific outlook. Even the most souless secularist can certainly sympathize with that. To listen to the rhetoric of pan-scientism, you'd have to conclude that its supporters are unaware that science is a vanishingly tiny fraction of human experience. The question was asked "have you ever had an experience that you could not scientifically explain?" as if it weren't obvious that almost every experience is not reducible to some sort of scientific explanation--"spiritual" experience, which always seems to be exemplified by sighing at a beautiful vista, is nothing extraordinary in this regard. Most of what we do—hoping, enjoying, hurting, arguing, sympathizing, cursing, laughing, trying, playing—isn't captured by the sciences and can't be, not because of some defect of science but because science is about knowing about things in a particular way while living is comprised of all the ways we do and suffer. One can imagine an explanation of a joke that accurately and adequately described it in terms of atoms and void, but the explanation wouldn't be funny. Category mistake. The best screwdriver in the world is a lousy adverb.
Another job of "spirituality" is less complicated. One insists on possessing spirituality as a no-fuss, shorthand way of asserting "I am not a philistine." If most of these folks really weren't philistines, however, you'd think their spirituality would amount to more than a verbal gesture about oneness with the all. Except for the odd mystic, however, who spends appreciable time communing the cosmos anyhow? Well, experiencing the unity of all things has this much going for it: it requires no complicated or expensive equipment or time-consuming training, you can do it anywhere, and nobody can prove you're faking it.
One small cavil: it's cheating to think that the absence of spirits is an objection to spirituality since the whole point of claiming that you're a spiritual person, as opposed, for example, to a Methodist, is that vaguing things out gets around the necessity of making unlikely empirical claims about the reality of ghosts or angels. That's part of the job of "spirituality."