Wiktionary
flat-earther
alt. 1 A person who believes or advocates the theory that the planet Earth is flat. 2 (context idiomatic by extension English) A person who believes or advocates an outlandish, discredited theory; a person who refuses to acknowledge the truth despite overwhelming evidence. n. 1 A person who believes or advocates the theory that the planet Earth is flat. 2 (context idiomatic by extension English) A person who believes or advocates an outlandish, discredited theory; a person who refuses to acknowledge the truth despite overwhelming evidence.