Source : Webster's Revised Unabridged Dictionary (1913)

Referendum \Ref`er*en"dum\, n.; pl. {-da}. [Gerundive fr. L.
   referre. See {Refer}.]
   The principle or practice of referring measures passed upon
   by the legislative body to the body of voters, or electorate,
   for approval or rejection, as in the Swiss cantons (except
   Freiburg) and in various local governments in the United
   States, and also in the local option laws, etc.; also, the
   right to so approve or reject laws, or the vote by which this
   is done. Referendum is distinguished from the mandate, or
   instruction of representatives by the people, from direct
   government by the people, in which they initiate and make the
   laws by direct action without representation, and from a
   plebiscite, or popular vote taken on any measure proposed by
   a person or body having the initiative but not constituting a
   representative or constituent body.

Referendum \Ref`er*en"dum\ (r?f`?r*?n"d?m), n. [Gerundive fr. L.
   referre. See {Refer}.]
   1. A diplomatic agent's note asking for instructions from his
      government concerning a particular matter or point.

   2. The right to approve or reject by popular vote a meassure
      passed upon by a legislature.

Source : WordNet®

referendum
     n : a legislative act is referred for final approval to a
         popular vote by the electorate
     [also: {referenda} (pl)]