Definition of "nonspectral"

I notice that each of the myriad towel carts on the Dreamward’s Deck 12 is manned by its very own Towel Guy, and that their Towel Guys are ruddily Nordic and nonspectral and have nothing resembling withering neutrality or boredom about their mien.

1997, David Foster Wallace, “A Supposedly Fun Thing I'll Never Do Again”, in A Supposedly Fun Thing I'll Never Do Again, Kindle edition, Little, Brown Book Group