A person who gainsays; someone who contradicts, denies, or argues against something.
From 'gainsay' plus the agent suffix '-er,' creating a noun for one who performs the action of contradicting or denying. This word has roots in Middle English and Old Norse through its verbal ancestor.
A gainsayer is a professional arguer or skeptic—someone who always says no! The medieval use of this term shows that people have always had critics and contrarians, and back then they needed a fancy word for them.
Complete word intelligence in one call. Free tier — 50 lookups/day.