Pounds per square inch indicates the amount of pressure imposed on an object, as well as the maximum amount of pressure an object can withstand. For example, a tire may be inflated to 26 psi, but the maximum pressure the tire may withstand is 40 psi.
After retiring from the National Basketball Association, Michael Jordan surprised the sports world by signing a minor league baseball contract with the Chicago White Sox. He reported to spring training and was assigned to the MLB team. He played 17 games with the White Sox before the organization sent him to the Birmingham Barons on March 31, 1994.
[added from my comment: According to Baseball Reference, Michael Jordan was 31 when he played one season as an outfielder for the Birmingham Barons, which were a AA minor league affiliate of the Chicago White Sox. (for context, AA is the second-highest minor league level; AAA is the only step between AA and the Major League).