1. To be idle or do something without much purpose. Quit mucking around and help me take out the trash! After the stressful week that I had, I'm looking forward to just mucking around the house for the weekend. What are you doing mucking around with those knuckleheads? You're going to get into trouble.

2. To meddle, interfere, or tweak, often in an uncareful or casual way. Please don't muck around with the thermostat, I have it set exactly the way I want it. I've been mucking around with the melody but haven't been able to get it quite right.