loose cannon
idiom

A person who behaves unpredictably and can cause trouble
  • 1The new employee is a loose cannon, always doing things his own way.
  • 2Be careful with Jake; he's a loose cannon and might say something inappropriate.
A loose cannon is someone who acts in a way that is hard to predict and can create problems. They might do things without thinking about the consequences, which can lead to trouble for themselves and others.
Card
Remember, a loose cannon is like a wild card in a deck of cards - you never know what they might do next! Stay cautious and be prepared for anything when dealing with someone who is a loose cannon.
in the barnyard
Unpredictable Behavior
Amanda
Did you see how Tom let the chickens out again?
Jessica
Yeah, he's such a loose cannon sometimes.
Amanda
I know, we never know what he'll do next.
Jessica
Let's hope he doesn't decide to mess with the tractor.
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Similar to "loose cannon":
  • 1unpredictable person
  • 2wild card