subscriber

noun3

1. •
   A person who subscribes to a publication or a service.

   • Our magazine has over ten thousand subscribers.
2. •
   A system or component that subscribes to something, such as an event, made available by a publisher.

   • An event aggregator facilitates a fire-and-forget model of communication. The object triggering the event doesn't care if there are any subscribers. — 2013
3. •
   A person undersigned.