Source : Webster's Revised Unabridged Dictionary (1913)

Shibboleth \Shib"bo*leth\, n. [Heb. shibb[=o]leth an ear of
   corn, or a stream, a flood.]
   1. A word which was made the criterion by which to
      distinguish the Ephraimites from the Gileadites. The
      Ephraimites, not being able to pronounce sh, called the
      word sibboleth. See --Judges xii.

            Without reprieve, adjudged to death, For want of
            well pronouncing shibboleth.          --Milton.
      Also in an extended sense.

            The th, with its twofold value, is . . . the
            shibboleth of foreigners.             --Earle.

   2. Hence, the criterion, test, or watchword of a party; a
      party cry or pet phrase.

Source : WordNet®

shibboleth
     n 1: a favorite saying of a sect or political group [syn: {motto},
           {slogan}, {catchword}]
     2: a manner of speaking that is distinctive of a particular
        group of people