A person who doesn't say "Bless you" or "Gesundheit" after hearing someone else sneeze and anyone who ignores or prefers not to receive such a response after sneezing.
Greg cringes at work after sneezing when the chorus of "bless you", "bless you" rolls in. He sneezes a couple of times most mornings in his process of waking up after getting to work. He finds his coworkers annoying in their ritual and has become a "Sneeze Atheist".