Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
Informal foolish, mischievous, or deceitful tricks or behavior
Used by arrangement with John Wiley & Sons, Inc.
noun SlangThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Silly, mischievous, or deceitful acts or behavior.
monkey business - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Silly, mischievous, or deceitful conduct, as in The teacher told the children to cut out the monkey business and get to work, or I don't trust that lawyer—there's some monkey business going on. This expression transfers the tricks of monkeys to human behavior. [Late 1800s]