Definition of muck up in English:

muck up

phrasal verb

Australian, NZ
informal
  • Behave badly; mess around.

    ‘boys are more likely to muck up at what they see as poor teaching’
    • ‘There are many things that can distract a driver, and kids and pets mucking up in the backseat is a classic.’
    • ‘He spent most of his time shouting at me because I was always mucking up and answering back.’
    • ‘They can muck up, and make fun, and even make your life hard.’
    • ‘Even though he mucks up all the time, he gets away with it because the teachers think of him as some sort of eccentric genius.’
    • ‘If you muck up, you're automatically eligible for three months jail.’
    • ‘They fear you might use the certainty of a weekly wage to start mucking up again.’
    • ‘What does a court do where one of the parents deliberately mucks up?’
    • ‘If you muck up again it becomes a criminal charge.’
    • ‘There've been numerous other similar incidents this year of footballers mucking up in public.’
    • ‘With the boss away, he steps up to umpire the hour when the kids muck up for the cameras.’