Definition of a tough (or hard) nut to crack in English:

a tough (or hard) nut to crack

phrase

informal
  • A difficult problem or an opponent that is hard to beat.

    • ‘Upgrading a module that combines PHP with SQL is a tougher nut to crack, and it seems as though the XOOPS people have done an admirable job.’
    • ‘Nine-year-olds are tough nuts to crack, as Peter Loraine, head of marketing at S Club Juniors' label Polydor, points out.’
    • ‘He should prove a tough nut to crack over tomorrow's extended three miles.’
    • ‘I'm sure BB would like to implement something that works well for everyone, but it's a very difficult nut to crack and not something to rush into.’
    • ‘Oliver Cromwell ordered the walls to be ‘slighted’ - pulled down in parts so that if hostilities broke out again it would not prove so tough a nut to crack.’
    • ‘Japan has proved a tough nut for Microsoft's console division to crack.’
    • ‘But he's right about parents being a tougher nut to crack.’
    • ‘‘Entertainment is a really, really difficult nut to crack,’ admits Bolland.’
    • ‘But reforming the media through policy changes may be the toughest nut to crack in the entire U.S. political system.’
    • ‘Now they, like the rest of Europe, are tough nuts to crack.’