A person who questions the validity or authenticity of something purporting to be factual.
From M.Fr. sceptique and directly from L. scepticus "the sect of Skeptics," from Gk. skeptikos "thoughtful, inquiring" (plural Skeptikoi "the Skeptics, followers of Gk. philosopher Pyrrho," who lived c. 360-270 B.C.). from skeptesthai "to reflect, look, view," → spectrum.
1) Inclined to skepticism; having an attitude of doubt.
1) A doubting or questioning attitude or state of mind.