Definition of melt down in US English:

melt down

phrasal verb

  • 1Collapse or break down disastrously.

    ‘many expected him to melt down at the first sign of trouble’
    • ‘The case was worth deciding this way, just to witness otherwise sensible intelligent academics melt down.’
    • ‘Ned Yost seemed to melt down at the end of last season.’
    • ‘But day after day, the enthusiasm is melting down.’
    • ‘In spite of history-making efforts by governments around the world, financial markets everywhere are still melting down.’
    • ‘Next thing you know, her campaign melts down.’
    • ‘Well, day four of her confirmation hearings, and the woman is not melting down.’
    • ‘In fact, they delayed finalizing the satellite deal, which was announced last September just as the economy was melting down.’
    • ‘During the past century empires crashed, new states foundered, utopian projects failed and entire civilisations melted down.’
    • ‘The recent site melt down has allowed me to repost this article with several more images.’
    • ‘Just letting Citigroup melt down could have been catastrophic.’
  • 2(of a nuclear reactor) undergo a catastrophic failure as a result of the fuel overheating.

    ‘if the pumps that cool the reactor core become disabled the core could begin to overheat, and the reactor could melt down’
    • ‘Many expected him to melt down at the first sign of trouble.’