The term 'Pool Triangle' is a term used in the game of billiards. It is also known as a 'RACK, ' which is a four-letter word. The Pool Triangle is a triangular-shaped device used to arrange the balls at the start of a game. It is placed on the table and the balls are arranged inside it in a specific pattern. The triangle is then removed and the balls remain in the same position. This allows for a fair and consistent start to the game.