monkey business

noun

1. frivolous or mischievous behavior.

2. improper or underhanded conduct; trickery.

monkey business

noun

1. informal,  mischievous, suspect, dishonest, or meddlesome behaviour or acts

Word History and Origins

Origin of monkey business¹

An Americanism dating back to 1880–85

Idioms and Phrases

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]