The Collaborative International Dictionary of English v.0.48:

Forerunner \Fore*run"ner\, n.
   1. A messenger sent before to give notice of the approach of
      others; a harbinger; a sign foreshowing something; a
      prognostic; as, the forerunner of a fever.
      [1913 Webster]

            Whither the forerunner in for us entered, even
            Jesus.                                --Heb. vi. 20.
      [1913 Webster]

            My elder brothers, my forerunners, came. --Dryden.
      [1913 Webster]

   2. A predecessor; an ancestor. [Obs.] --Shak.
      [1913 Webster]

   3. (Naut.) A piece of rag terminating the log line.
      [1913 Webster]

WordNet (r) 3.0 (2006):

forerunner
    n 1: a person who goes before or announces the coming of another
         [syn: precursor, forerunner]
    2: something that precedes and indicates the approach of
       something or someone [syn: harbinger, forerunner,
       predecessor, herald, precursor]
    3: anything that precedes something similar in time; "phrenology
       was an antecedent of modern neuroscience" [syn: antecedent,
       forerunner]