1. Быть (гражданином), потому что вы родились в стране.
Mr. and Mrs. Schmidt came to the United States from Germany and are naturalized citizens but their children are natural-born citizens.
2. Родиться с большими способностями стать (кем-либо); практически с самого начала обладать большими способностями (например, в спорте или искусстве).
Joe had never played baseball before trying out for the team but he showed that he was a natural-born pitcher and he became the best in the league.
Mozart was a natural-born musician. He could play the piano well when he was only six years old.