Commit to a course of action; make a final decision about a course of action. Derived from U.S. Navy terminology for a naval aviator confirming he has the optical landing aids in sight prior to landing on an aircraft carrier.
Famously used during the movie "Top Gun". Flight Control: "Maverick, you're at 3/4 of a mile. Call the ball." Maverick: "Roger. Maverick has the ball."