Ballpark has two common meanings that connect in an interesting way:

A ballpark is a stadium or field where baseball is played. When fans fill the seats at a ballpark on a sunny afternoon, they're gathering to watch their team compete. Famous ballparks like Fenway Park in Boston or Wrigley Field in Chicago have hosted games for over a century.

The word also means an approximate range or rough estimate. When someone asks for a ballpark figure on how much a new bike costs, they want a general idea, not an exact price down to the penny. If you're planning a school fundraiser and someone asks how many people might attend, you might give a ballpark estimate: “probably somewhere in the ballpark of 200 people.”

When something isn't even in the ballpark, it's not even close. If someone guesses your new bike costs $5 when it actually costs $500, that guess isn't in the ballpark at all.