In·cheon also In·chon (?n?ch?n?, -ch?n?) A city of northwest South Korea on an inlet of the Yellow Sea southwest of Seoul. It was opened to foreign trade in 1883.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.