Definition of grind
When we talk about the "grind" in poker, we are talking about the life of a regular poker player, a pro player who makes his living with poker. In the idea of the grind, there is the idea of the long and hard work, the constant effort, the relentlessness, the small but steady payout. A grinder is a player who "grind", that is, who plays several tables simultaneously and plays long hours. A grinder is a player who works hard for his or her winnings. He is reliable, consistent, hardworking and wins on a regular basis.
The image of a grinder
The word "grinder" in English is a tool that grinds (like a coffee grinder, a tool that grinds coffee beans) or a tool that saws, but little by little. If we want to cut a very strong padlock, we can use a grinder, a tool that will cut the metal efficiently, but slowly. The grind necessarily has a pejorative connotation. The grinder is not a poker millionaire, he is a player who pays his bills with his poker, but he will have modest winnings that he will accumulate quietly. The grinder is still a solid player. He is considered a serious and winning player.