Taki's Magazine had a fun article by the legendary Joe Bob Briggs, who's sick of hearing about people being "spiritual but not religious."  After due consideration, he concludes that the phrase really means you're atheist.

To me, religious means you go to church.  For decades, I didn't go to church.  That made me "not religious."  Spiritual, in my vocabulary, means you believe in God.  If you're a Westerner, you probably also believe in Jesus from some long-ago didn't-take-too-well forced churchgoing.  This was I.

But I didn't go to a Christian (or any other) church, mainly because the pious faces and oozing, unctuous concern smacked of modern liberalism.  I couldn't stand those guys from an early age, even if we didn't call them "liberals."  I couldn't pin it down then, but today I realize they were religious but not spiritual.  Because of them, organized spirituality was for me a major turnoff.

I also held, and still do, that the only difference between modern liberals and old-time fire-and-brimstone believers is that libs are too, um, sophisticated to believe in Brother Love's Traveling Salvation Show.  Grandma's and Grandpa's religion wasn't cool.  I also hold that antecedent to these wretches came the Salem witch-burners, the progressives of their day.  The burners, not the burned.

At any rate, I was spiritual but not religious.  Today, I see that I was a Christian all along whose gripe was with phony Christians.  To me, that phrase does mean something, and it ain't atheist.  It means somebody's not doing the religious part right.

I agree, however, that a whole lot of people today use spiritual-but-not-religious to sound New Age or hip or cool.  Paul McCartney, after all, claims to be spiritual but not religious.  Not speaking for Macca, but most people I've seen who claim that status are too yellow to commit one way or another.  They just like the faintly rebellious sound of it.