I like "subtle matter", personally. It isn't just light, as far as we know baryonic matter also passes through without interacting in any measurable way. It h

I like "subtle matter", personally. It isn't just light, as far as we know baryonic matter also passes through without interacting in any measurable way. It has certain... resonances with mystic traditions such as Theosophy, and I could see that being unwelcome in some circles. To my taste it's perfect.