The Collaborative International Dictionary of English v.0.48:

Subscriber \Sub*scrib"er\, n.
   1. One who subscribes; one who contributes to an undertaking
      by subscribing.
      [1913 Webster]

   2. One who enters his name for a paper, book, map, or the
      like. --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

subscriber
    n 1: someone who expresses strong approval [syn: subscriber,
         endorser, indorser, ratifier]
    2: someone who contracts to receive and pay for a service or a
       certain number of issues of a publication [syn: subscriber,
       reader]
    3: someone who contributes (or promises to contribute) a sum of
       money [syn: subscriber, contributor]