Meaning of flat-earther

flat-earth•er

Pronunciation: (flat'ûr'thur), [key]
— n.
  1. a person who adheres to the idea that the earth is flat.
  2. a person who clings to an idea or theory that has long been proved wrong.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.