verb (v)

• manage in a makeshift way; do with whatever is at hand(verb.social)

  Synonym:
  improvise
  

  source: wordnet30
• perform without preparation(verb.creation)

  Example:
  He extemporized a speech at the wedding.
  

  Synonym:
  ad-lib, extemporise, improvise, improvize
  

  source: wordnet30
• To speak extempore; especially, to discourse without special preparation; to make an offhand address.(verb)

  source: webster1913
• 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.(verb)

  source: webster1913