The Collaborative International Dictionary of English v.0.48:

Prorogation \Pro`ro*ga"tion\, n. [L. prorogatio: cf. F.
   prorogation.]
   1. The act of counting in duration; prolongation. [Obs.]
      --South.
      [1913 Webster]

   2. The act of proroguing; the ending of the session of
      Parliament, and postponing of its business, by the command
      of the sovereign. [Eng.]
      [1913 Webster]

   Note: After an adjournment all things continue as they were
         at the adjournment; whereas, after a prorogation, bill
         introduced and nut passed are as if they had never been
         begun at all. --Mozley & W.
         [1913 Webster]

WordNet (r) 3.0 (2006):

prorogation
    n 1: discontinuation of the meeting (of a legislative body)
         without dissolving it