The nuts is a poker term for the best hand in a specific situation. This doesn’t have to be a Royal Flush, but it has to be the best-ranking hand under the circumstances. This term is prevalent in community card poker games like Texas Hold’em and Omaha.
For example, let’s say you have AsJs, and the flop comes Qs 7s 3s. In this case, you have the nut flush, which is the best possible hand in this situation. However, if the turn pairs the board and is Qc, you do not have the nuts anymore since the best possible combination is quad queens.