The Collaborative International Dictionary of English v.0.48:

Plebiscite \Pleb"i*scite\, n. [F. pl['e]biscite, fr. L.
   plebiscitum.]
   A vote by universal male suffrage; especially, in France, a
   popular vote, as first sanctioned by the National
   Constitution of 1791. [Written also plebiscit.]
   [1913 Webster]

         Plebiscite we have lately taken, in popular use, from
         the French.                              --Fitzed.
                                                  Hall.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

PLEBISCIT, civil law. This is an anglicised word from the Latin plebiscitum,
which is composed or derived from plebs and scire, and signifies, to
establish or ordain.
     2. A plebiscit was a law which the people, separated from the senators
and the patricians, made on the requisition of one of their magistrates,
that is, a tribune. Inst. 1, 2, 4.