A dignitary is a very important person (VIP), usually from another country. Major dignitaries from other countries might get to meet the President when they visit the U.S.
If you see the word dignity in dignitary, it gives you a clue to its meaning. When we treat people with dignity, we're treating them with respect. Dignitaries get a lot of respect, because they're important and powerful people in their country — heads of state, ambassadors, and royalty are all dignitaries. It's not easy to become a dignitary: you'd better either be born into the right family or become a powerful person in some other way.
