Noun
(chiefly derogatory) A person who lives at, lived at, or was raised by someone at a low altitude or from any city. A person not raised in or by someone directly from high mountain areas. (used by those who were born, raised, and are still living in higher altitude non-city or city like areas).
(Western US, especially in the Rocky Mountains) Anyone from the East; anyone from outside the Rockies.
(Appalachia) Any outsider to Appalachia.
(northern central Pennsylvania) Anyone from southern Pennsylvania (particularly around Philadelphia), New Jersey, or other low-lying areas outside the Alleghenies / Appalachians.
(northern New England) Any non-native, but particularly one from southern New England (including Massachusetts), downstate New York, or New Jersey.
(Upper Peninsula of Michigan) Anyone from Wisconsin.
(Northern Michigan) Anyone from lower Michigan (those below Mt. Pleasant).
(lower Michigan) Anyone from Indiana or Ohio.
(Wisconsin) Anyone from Illinois.
(Canada) Anyone from Saskatchewan.
(Georgia) Anyone from Florida.
(Central Coast NSW) Anyone from Umina.
(physics) An inhabitant of or observer in a universe with two spatial dimensions.
(cycling) A flatland BMX rider.
Source: en.wiktionary.orgA common title for people born on Earth is "Flatlander"; having been born and raised in the only environment in Known Space to which humans are well-adapted, they are considered naïve and a bit helpless by humans from colony worlds. Source: Internet
Michael lives on a " Flatlander " diet, meaning that he eats only things that are two dimensional; this began after a period during which he barred himself in his office, eating only what his co-workers slid under the door. Source: Internet
This tension is expressed in the terms, "Woodchuck", being applied to those established in the state, and "Flatlander", applied to the newcomers. citation Vermont is the least populous New England state. Source: Internet
Imagine our Flatlander doesn’t live on a perfect sphere, but rather on a flattened disk, like a ball with most of its air let out. Source: Internet