In baseball, the abbreviation "BB" refers to "bases on balls." This occurs when a batter is allowed to proceed to first base after four called balls by the home plate umpire during a single at-bat.
Batters hit by a single pitch are also given first base without the possibility of being ruled out, designated as "HBP" on the score sheet. While the free base is most commonly referred to as a "walk," players generally jog down the first base line. Baseball's all-time hit king, Pete Rose, earned the nickname "Charlie Hustle" for his tendency to run to first base on the majority of his 1,566 career walks.