Definition of blue Monday in English:

blue Monday

noun

informal
  • 1A Monday on which one feels gloomy or dispirited, especially because one has to return to work after the weekend.

    ‘remember that when you're having a blue Monday, just climbing out of bed is a positive start’
    • ‘It's a blue Monday and the weekend had not been so good either because the golf course was flooded.’
    • ‘For him, tomorrow will be a particularly blue Monday; his firm scrapped a €200 million flotation that would have valued him at €80 million.’
    • ‘It was another blue Monday for investors, with the share dropping 5% in early morning trade.’
    • ‘Between us we have written about almost every continent, hiked many a trail, sailed a few seas—and also wrestled with canceled flights and occasionally weathered blue Mondays.’
    • ‘They experienced a blue Monday as investors sent the stock plunging by close to 30% in midday trade.’
    • ‘It's Monday, perhaps a blue Monday at the start of the week, so maybe you all need cheering up a bit.’
    • ‘The evening before they dined out on fine Italian cuisine to alleviate any worries of a blue Monday.’
    • ‘It was a blue Monday for the company when a newspaper printed five suggestions why consumers shouldn't buy its upcoming console.’
    • ‘Monday, blue Monday, came as it must.’
    • ‘Four plates we wanted to try were eighty-sixed; clearly it was definitely a blue Monday.’
    1. 1.1British (in the northern hemisphere) a Monday in January, typically the third Monday of the month, that is characterized as the most depressing day of the year.
      ‘snow and ice brought travel chaos across the UK on Blue Monday’
      • ‘For those struggling with Blue Monday, tips for getting through it include capitalising on nature by making sure to spend as much time outside as possible and doing exercise.’
      • ‘Since the idea of Blue Monday has become well known he has admitted the idea of a single most depressing day was 'not particularly helpful' because it became 'a self-fulfilling prophecy'.’
      • ‘January 18 was officially Blue Monday, when huge swathes of the population are said to be suffering from depression after Christmas excesses, debts, going back to work, and miserable weather.’
      • ‘According to commentators, Blue Monday leaves its sufferers feeling down or, in some cases, depressed.’
      • ‘Several publications offer tips to emerge from Blue Monday—as it's been dubbed—with a smile.’
      • ‘After a weekend of sad and troubling news, Plymouth is waking up today to a very wet and windy Blue Monday.’
      • ‘There's no better way to banish the January blues than by instantly lifting the spirits with a feel-good movie and even Blue Monday is no match for our mood boosting top 10.’
      • ‘The mist appeared in Derbyshire on 'Blue Monday'.’
      • ‘A wide shot of the polar ices or ideas on how to brighten your Blue Monday might not change your life but there's very clearly a good amount of not too intrusive content on the page to greet you.’
      • ‘Tomorrow is Blue Monday—when gloomy weather, post-Christmas bills, and failure of our New Year resolutions are said to make us the most miserable we'll feel all year.’
      • ‘As it's Blue Monday, why not pass this on to someone to cheer them up.’

Origin

Late 18th century: originally in German contexts, in reference to a Monday during which people chose not to work, especially as a result of excessive indulgence over the course of the weekend (the reason why such a Monday should be described as blue is not clear). The modern meanings derive from blue in the sense ‘melancholy, sad, or depressed’ (see blue (sense 2 of the adjective).