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

a tough (or hard) nut

phrase

informal
  • Someone who is difficult to deal with; a formidable person.

    • ‘In the MacTavish Cup first-round replay, Loch Carron's difficulties against Kilmallie continued and they found them once again a tough nut.’
    • ‘The programme needed a strong story line and, being a bit of a tough nut anyway, she could live with that, she said.’
    • ‘John Cena, the current WWE World Champion, is known around the world as a tough nut, but with the release of his new LP, he may be getting some respect as an MC as well.’
    • ‘Romanov is by all accounts a hard nut, not inclined to throw good money after bad.’
    • ‘And you look at them and you think, ‘OK, this is going to be a hard nut.’’
    • ‘While Spider-man, Daredevil, X-Men, Hulk and Blade were a slam dunk from an entertainment standpoint, the central figure of the current cinematic outing is something of a tough nut.’
    • ‘That's a hard nut and I'm not prepared to say where all those should be, but I think there are places where they may be needed.’
    • ‘The female of the species are supposed to be tough nuts.’
    • ‘Schumacher may be a tough nut, yet with hindsight that could prove to be a key moment when the drivers line up in Malaysia for the last grand prix of the season on October 22.’
    • ‘Clarke, who died in 1990, was a tough nut in his own right.’