red-light district (r?d?l?t?)n. A neighborhood containing many brothels and often other businesses related to sexual gratification, such as sex shops and peepshows.[Perhaps from the red lanterns or lights said to have been placed in the windows of American brothels in the 1800s.]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.red?-light? dis`trict n. an area or district in a city in which many houses of prostitution are located. [1890?95; allegedly so called because brothels displayed red lights] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.