Full explanation — Rainbow Board
A rainbow board is a flop where all three community cards are of different suits, meaning no flush draw is immediately possible. For example, A♠ 7♥ 3♦ is a rainbow flop. This board texture is considered 'dry' or uncoordinated, as it greatly reduces the number of immediate draws an opponent might hold. Such boards often favor pre-flop aggressors, allowing for smaller and more frequent continuation bets (c-bets) to pressure opponents, as there's less risk of being outdrawn by a flush. They also tend to reduce multi-way action.