C2 [ C ] a person who will legally receive money, property, or a title from another person, especially an older member of the same family, when that other person dies:
The guest of honour was the Romanov heir to the throne of all Russia.
Despite having a large family, they still had no son and heir.
[ C usually singular ] someone who now has responsibility for dealing with a problem or situation that existed or was created earlier:
The French finance minister is heir to a tradition of central control that goes back to Louis XIV.
[ C usually singular ] someone who continues to do the work of someone important who has died, or someone who has the same position as the previous person who held that position