Sam Harris reclaims "spiritual" for unbelievers:
The word “spirit” comes from the Latin spiritus, which in turn descends from the Greek pneuma, meaning “breath.” Around the 13th century, the term became bound up with notions of immaterial souls, supernatural beings, ghosts, etc. It acquired other connotations as well—we speak of the spirit of a thing as its most essential principle, or of certain volatile substances and liquors as spirits. Nevertheless, many atheists now consider “spiritual” thoroughly poisoned by its association with medieval superstition.
I strive for precision in my use of language, but I do not share these semantic concerns. And I would point out that my late friend Christopher Hitchens—no enemy of the lexicographer—didn’t share them either. Hitch believed that “spiritual” was a term we could not do without, and he repeatedly plucked it from the mire of supernaturalism in which it has languished for nearly a thousand years.