sceptic

Noun

skeptic (plural skeptics)

1. (US) Someone who doubts beliefs, claims, plans, etc. that are accepted by others as true or appropriate, especially one who habitually does so.
   • But for the fly he might have made me think He had been at his poetry , comparing Nailhead with fly and fly with huckleberry : How like a fly , how very like a fly . But the real fly he missed would never do ; The missed fly made me dangerously skeptic.[…]1997, Robert Faggen, Robert Frost and the Challenge of Darwin, University of Michigan Press, →ISBN, →LCCN, →OCLC, page 98
2. (US) Someone who is skeptical towards religion.

See all 3 meanings of skeptic