Just define "spiritual" as something other than "supernatural". Life contains aspects of a numinous or sacred quality, even if there is no Absolute, supernatural basis for that quality.

I have an affinity for some of the teachings of Buddhism and Christianity. If someone asks me at the bar, I'd say I'm "spiritual, but agnostic and ultimately not religious"...or something like that.

In my experience, definitions get tricky when dealing in the atheist/agnostic/ignostic space.