The Collaborative International Dictionary of English v.0.48:

John \John\ (j[o^]n), n. [See Johannes.]
   A proper name of a man.
   [1913 Webster]

   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.] (Zool.) 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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "John Doe":
   Everyman, Jane Doe, Public, Richard Roe, alias, anonym,
   assumed name, body politic, citizenry, common man, commonwealth,
   community, community at large, estate, everybody, everyman,
   everyone, everywoman, false name, fictitious name, folk, folks,
   general public, gentry, men, nation, nationality, nom de guerre,
   nom de plume, nom de theatre, pen name, people, people in general,
   persons, polity, populace, population, professional name,
   pseudonym, public, society, stage name, state, world, you and me