A rough numerical estimate or approximation. Ballpark figures are commonly used by accountants, salespersons and other professionals to estimate current or future results. A stockbroker could use a ballpark figure to estimate how much money a client might have at some point in the future, given a certain rate of growth.allpark figures are commonly used by accountants, salespersons and other professionals to estimate current or future results. A stockbroker could use a ballpark figure to estimate how much money a client might have at some point in the future, given a certain rate of growth.