Definition of crack up in US English:

crack up

phrasal verb

informal
  • 1Suffer an emotional breakdown under pressure.

    • ‘Many of us are visibly cracking up after serving two years.’
    • ‘I was short-tempered and I was cracking up a bit under the pressure of it all.’
    • ‘His stylish arthouse flick looks at three women as they crack up.’
    • ‘He left the club having exhibited signs that he was cracking up under the strain months before.’
    • ‘The guys had cracked up so hard, but I was just very traumatized.’
    • ‘‘If I had not had Diana and the children I would have cracked up and had a mental breakdown by now,’ he said.’
    break down, have a breakdown, lose control, be overcome, collapse, go to pieces, go out of one's mind, go mad, crumble, disintegrate
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  • 2Burst or cause to burst into laughter.

    • ‘We were laughing so hard that we just fell over cracking up, unable to control ourselves any longer.’
    • ‘He heard the whole class with the exception of her friends crack up laughing.’
    • ‘Luckily, it's hard to get too stressed when you're trying to stop yourself cracking up with laughter.’
    • ‘This time I can't hold back my laughter and I crack up.’
    • ‘Melissa narrowed her eyes and glared at the two guys, who were cracking up with laughter.’
    • ‘He shut the door in his face and led Mystie back to his room where they cracked up and collapsed on his bed.’
    • ‘Then without warning, instead of blowing up, she started cracking up in hysterical laughter.’
    • ‘Beth cracks up and falls back down onto the towel.’
    • ‘Before I knew it I was buzzed and cracking up with laughter.’
    • ‘Ancestral forms of play and laughter existed in other animals long before humans began cracking up.’
    • ‘I could tell the elder student wanted to crack up in laughter about then, but prevented himself from doing so with a mere smile.’
    • ‘Lila said and the girls started cracking up with laughter.’
    • ‘All it takes is for one person to crack up and we all collapse.’
    • ‘I really cracked up in laughter when I read the headline ‘Protest is the backbone of democracy’.’
    • ‘He cracks up into laughter, his shoulders heaving uncontrollably.’
    • ‘He blushed furiously, and Alex cracked up with laughter.’
    • ‘Kayla heard them cracking up into laughter from her spot in the kitchen.’
    • ‘Stuart standing there is too much for the security guard and he cracks up laughing.’
    • ‘Jules mouth was hanging open while Brad looked like he would burst out cracking up any moment.’
    • ‘"Oh Jesus " Alice said wearily and then cracked up laughing.’
    burst out laughing, dissolve into laughter, roar with laughter, shake with laughter, laugh uncontrollably, guffaw, be doubled up, split one's sides, hold one's sides
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