Lewis & Short

prōrŏgātĭo, ōnis, f. [prorogo].

  1. I. A prolonging, extension of a term of office: prorogatio imperii, a prolongation of one’s command, Liv. 8, 26 fin.
  2. II. A putting off, deferring of an appointed time: diei, Cic. Att. 13, 43 (in Cic. Mur. 23, 47, the true reading is perrogationem; in Liv. 42, 30, 9, propagatio).