fool with

fool with (someone or something)

1. To play or tinker with something, often in an aimless manner. Hey, don't fool with the thermostat—it needs to stay at 68 degrees. Grandpa's still fooling with that old radio, but I doubt he'll get it to work again.
2. To engage in aimless recreation or frivolous time-wasting with someone or something. Quit fooling with the dog and work on your book report already!
3. To tease, mock, or bully someone. Sarah's a very sensitive kid, so don't fool with her. If you keep fooling with me like that, you're going to get a punch in the nose!
4. To interfere, associate, or become involved with someone or something, especially when doing so is dangerous. He's going to get himself killed if he keeps fooling with those gangsters. You're fooling with political forces beyond your understanding.
See also: fool
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

fool (around) with someone or something

 
1. to waste time in the company of someone or a group. Stop fooling around with those guys. They're up to no good most of the time. Better not fool around with part-time work. Go get a good job if you can.
2. to have dealings with or tamper with someone or something. You had better not fool around with my little sister. Don't fool with that thing!
3. to challenge or threaten someone or something. You had better not fool around with me, if you know what's good for you. Don't fool with the police force!
See also: fool
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

fool with

v.
1. To alter something improperly: Did someone fool with the computer settings?
2. To tease someone: Don't mind your uncle—he's just fooling with you.
See also: fool
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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The March fool with another month added to his folly." - Ambrose Bierce, The Devi's Dictionary
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