Pirate's Brew is a term used to describe an alcoholic beverage, usually made with rum and water. It is also known as GROG, which is the four-letter answer to the crossword puzzle. GROG was popular among sailors in the 18th century and was often served on long voyages. The rum was mixed with water to make it last longer and to prevent scurvy. The mixture was also known to have a calming effect on the crew.