runner

A person who moves, on foot, at a fast pace, especially an athlete.

Any entrant, person or animal (especially a horse), for a race or any competition; a candidate for an election.

A competitor in a poker tournament.

Somebody who controls or manages (e.g. a system).

A person or vessel that runs blockades or engages in smuggling.

A player who runs for a batsman who is too injured to run; he is dressed exactly as the injured batsman, and carries a bat.

A baserunner.

A person (from one or the other team) who runs out onto the field during the game to take verbal instructions from the coach to the players. A runner mustn't interfere with play, and may have to wear an identifying shirt to make clear his or her purpose on the field.

Anyone sent on an errand or with communications, especially for a bank (or, historically, a foot soldier responsible for carrying messages during war).

A restaurant employee responsible for taking food from the kitchens to the tables.