cop-out also cop·out (k?p?out?)n. Slang 1. A failure to fulfill a commitment or responsibility or to face a difficulty squarely.2. A person who fails to fulfill a commitment or responsibility.3. An excuse for inaction or evasion.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.cop?-out` n. 1. an act or instance of copping out. 2. a person who cops out. [1940?45] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.