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
    n 1: a room or building equipped with one or more toilets [syn:
         toilet, lavatory, lav, can, john, privy,
         bathroom]
    2: youngest son of Henry II; King of England from 1199 to 1216;
       succeeded to the throne on the death of his brother Richard
       I; lost his French possessions; in 1215 John was compelled by
       the barons to sign the Magna Carta (1167-1216) [syn: John,
       King John, John Lackland]
    3: (New Testament) disciple of Jesus; traditionally said to be
       the author of the 4th Gospel and three epistles and the book
       of Revelation [syn: John, Saint John, St. John, Saint
       John the Apostle, St. John the Apostle, John the
       Evangelist, John the Divine]
    4: a prostitute's customer [syn: whoremaster, whoremonger,
       john, trick]
    5: the last of the four Gospels in the New Testament [syn:
       John, Gospel According to John]