- a person who adheres to the idea that the earth is flat.
- a person who clings to an idea or theory that has long been proved wrong.
Origin of flat-earther
1930–35; flat earth + -er1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- informal a person who does not accept or is out of touch with the realities of modern life
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012