Source : Webster's Revised Unabridged Dictionary (1913)

Extemporize \Ex*tem"po*rize\, v. i. [imp. & p. p.
   {Extemporized}; p. pr. & vb. n. {Extemporizing}.]
   To speak extempore; especially, to discourse without special
   preparation; to make an offhand address.

Extemporize \Ex*tem"po*rize\, v. t.
   To do, make, or utter extempore or off-hand; to prepare in
   great haste, under urgent necessity, or with scanty or
   unsuitable materials; as, to extemporize a dinner, a costume,
   etc.

         Themistocles . . . was of all men the best able to
         extemporize the right thing to be done.  --Jowett
                                                  (Thucyd. ).

         Pitt, of whom it was said that he could extemporize a
         Queen's speech                           --Lord
                                                  Campbell.

Source : WordNet®

extemporize
     v 1: manage in a makeshift way; do with whatever is at hand;
          "after the hurricane destroyed our house, we had to
          improvise for weeks" [syn: {improvise}]
     2: perform without preparation; "he extemporized a speech at
        the wedding" [syn: {improvise}, {improvize}, {ad-lib}, {extemporise}]