to waste time doing something without a particular purpose.

The kids were just messing around at the mall.

Usage notes: often used in the not mess around - to act with a serious purpose:

Being a federal agent on the track of terrorists, Matt doesn't mess around.

• sit tight
• sitting duck
• sitting on top of the world
• sitting pretty
• sit up
• sit up and take notice
• sit well with
• sit well with someone
• six feet under
• six of one and half a dozen of the other
• six of one, and half a dozen of the other
• six of one, half a dozen of the other
• six of the best
• sixty-four-thousand-dollar question
• size up
• size up someone
• size up something
• skeleton in closet
• skeleton in cupboard
• skeleton in someone's closet
• skeleton in the closet
• skeleton in the cupboard
• skeleton in your cupboard
• sketch out
• sketch out something