Flat-earther
A person who believes the earth is flat
Example
he said satellites are fake and space isn’t real
wait, is he a flat-earther?
i think so… he sounded pretty serious
wow, that’s a whole different level
Flat-earther definition by Slang.net - The Slang Dictionary
This page explains what the slang term "Flat-earther" means. The definition, example, and related terms listed above have been manually compiled and written by the Slang.net team.
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A "flat-earther" is a person who believes the Earth is flat rather than spherical. While the idea itself dates back centuries, the modern term gained traction in the late 20th and early 21st centuries as online communities revived and spread flat Earth theories. The phrase is closely associated with groups like the "Flat Earth Society," which helped keep the concept in public conversation, especially as social media platforms made it easier for niche beliefs to gain visibility.
Today, people may use "flat-earther" both literally and figuratively in online discussions, memes, debates, and in person. Literally, it refers to people who genuinely hold the belief, but more commonly, people use it humorously or critically to describe someone who rejects widely accepted facts or believes in conspiracy theories.