Source : Webster's Revised Unabridged Dictionary (1913)

John \John\ (j[o^]n), n. [See {Johannes}.]
   A proper name of a man.

   {John-apple}, a sort of apple ripe about St. John's Day. Same
      as {Apple-john}.

   {John Bull}, an ideal personification of the typical
      characteristics of an Englishman, or of the English
      people.

   {John Bullism}, English character. --W. Irving.

   {John Doe} (Law), the name formerly given to the fictitious
      plaintiff in an action of ejectment. --Mozley & W.

   {John Doree}, {John Dory}. [John (or F. jaune yellow) +
      Doree, Dory.] (Zo["o]l.) An oval, compressed, European
      food fish ({Zeus faber}). Its color is yellow and olive,
      with golden, silvery, and blue reflections. It has a round
      dark spot on each side. Called also {dory}, {doree}, and
      {St. Peter's fish}.

Source : WordNet®

John Doe
     n 1: a hypothetical average man [syn: {Joe Blow}, {Joe Bloggs}, {man
          in the street}]
     2: an unknown or fictitious man who is a party to legal
        proceedings