Cracking the nut is most often used by land-based casino players. It is a phrase that refers to a player making enough money to cover their expenses and also make a profit on top of it. Simply put, it means to achieve projections.
The term might’ve derived from the phrase “tough nut to crack”, which refers to solving a difficult problem or dealing with a difficult situation.
While online casino players don’t have any gambling expenses, apart from losing bets, of course, those players who prefer playing in brick-and-mortar casinos often have to spend some money to possibly earn some in return.
For example, quite often, those expenses include travelling to and back from a casino, paying for a hotel in case they’re spending the night, and possibly even some drinks. For a player to “crack the nut”, they have to cover all those gambling-related expenses and then make a profit.