monkey business

Noun

monkey business (uncountable)

1. (idiomatic, informal) Activity that is mischievous, stupid, or time-wasting.
   • Stop all this monkey business and do your homework!
   • I’m going to take off the cuffs, Slim, and off you, Jerry. But don’t try any monkey business. When Peters answers the door, you tell him everything’s O. K., and that you’re the committee, see? Once the door’s open, we’ll do the rest.1918 December 10, J[oseph] Allan Dunn, “The Man With the Mole”, in Detective Story Magazine, volume XIX, number 5, New York, N.Y.: Street & Smith Corporation, →OCLC, chapter VIII (The End of Baldy)...

   Synonyms:

   badness, delinquincy, devilishness, devilment, devilry, deviltry, elfishness, goings-on, hanky-panky, impishness

2. (idiomatic, informal) Activity that is morally questionable or even mildly illegal.
   • She wondered what sort of monkey business her neighbour was up to, sneaking out of his house at 1:00 am.
   • If you ever hear a man talking about his duty as a citizen, by the Living Jingo dont trust him. … He's up to some kind of monkey business nine times out of ten. You dont know what a relief it is to me that you and Joe are comfortably settled in life.1925, John Dos Passos, “Revolving Doors”, in Manhattan Transfer, New York, N.Y.; London: Harper & Brothers, →OCLC, 3rd section, page 328

   Synonyms:

   hanky-panky, bad manners, badness, delinquency, devilishness, devilment, devilry, deviltry, disobedience, elfishness