A person who returns something, such as a borrowed item or a purchased product. The returner brought back the library books before the due date.
In sports, especially American football, a player who receives a kickoff or punt from the opposing team and attempts to advance it. The returner caught the kickoff and ran it back for a touchdown.
A person who comes back to a place after being away. The returner was greeted warmly by friends and family at the airport.