Source : Webster's Revised Unabridged Dictionary (1913)

Plenary \Ple"na*ry\, a. [LL. plenarius, fr. L. plenus full. See
   {Plenty}.]
   Full; entire; complete; absolute; as, a plenary license;
   plenary authority.

         A treatise on a subject should be plenary or full. --I.
                                                  Watts.

   {Plenary indulgence} (R. C. Ch.), an entire remission of
      temporal punishment due to, or canonical penance for, all
      sins.

   {Plenary inspiration}. (Theol.) See under {Inspiration}.

Plenary \Ple"na*ry\, n. (Law)
   Decisive procedure. [Obs.]

Source : WordNet®

plenary
     adj : full in all respects; "a plenary session of the
           legislature"; "a diplomat with plenary powers"