A "grand slam" in tennis refers to winning all four of the major championships in a single calendar year. These prestigious tournaments, known as the Grand Slam, consist of the Australian Open, French Open, Wimbledon, and US Open. Achieving a grand slam is extremely rare and represents the pinnacle of success in the sport. Only a few players, such as Rod Laver and Serena Williams, have accomplished this feat. Winning all four tournaments in a single year demonstrates unparalleled skill, consistency, and mental fortitude.