It means the main problem, difficulty or obstacle. This is from the Collins dictionary: there's the rub said to mean that there is a problem or contradiction which is difficult or impossible to deal with It is a common belief, that he will get things right in the end, given time. There's the rub. Time is always in desperately short supply in football these days. It comes from Shakespeare's Hamlet: When Hamlet was contemplating suicide, he said, ““To sleep; perchance to dream: ay there's the rub: for in that sleep of death what dreams may come?” So the problem is that we cannot know if death is even worse than life - are the nightmares you have when you're dead worse than the ones you have when you're alive?

Hi Dimin, This usage of "rub" is from Shakespeare. It's not that common in spoken English, but you read it once in a while. https://www.quora.com/Where-and-when-did-the-idiom-heres-the-rub-originate#:~:text=In%20%E2%80%9CHamlet%E2%80%9D%2C%20the%20title,grass%20surface%20or%20%E2%80%9Cgreen%E2%80%9D.

I'm a native speaker and I've never heard anyone use that phrase haha. Must be an old one.

It's a reference to a very famous quotation from Shakespeare. However, I've never heard it modified this way. When you see it, it is usually quoted directly as "Ay, there's the rub" or "There's the rub." Shakespeare's plays changed the English language. He added hundreds of new words and many idiomatic phrases. They are now part of the language and people sometimes use the phrases without knowing that they are from Shakespeare. I suspect that's what happened here. The writer picked up the phrase "There's the rub" from hearing it used. He didn't realize it was a quotation and that it shouldn't be changed. It is from the play "Hamlet," from a very famous speech called "Hamlet's soliloquy." A soliloquy is a speech made by a player, along on a stage, thinking out loud or talking to himself. Hamlet is thinking about committing suicide. He can't make up his mind. "To die, to sleep; To sleep: perchance to dream: ay, there's the rub; For in that sleep of death what dreams may come... Must give us pause..." What's the problem with suicide? According to Hamlet, the problem, "the rub," is that death might NOT be like sleep. He goes on to say that "the dread of something after death" makes it difficult to decide. Anyway, "there's the rub" is an idiomatic phrase. It is used in the context "Why not do X? Well, if you do that, what about problem Y? There's the rub."

He was