The Collaborative International Dictionary of English v.0.48:

Improvise \Im`pro*vise"\, v. t. [imp. & p. p. Improvised; p.
   pr. & vb. n. Improvising.] [F. improviser, it.
   improvvisare, fr. improvviso unprovided, sudden, extempore,
   L. improvisus; pref. im- not + provisus foreseen, provided.
   See Proviso.]
   1. To compose, recite, or sing extemporaneously, especially
      in verse; to extemporize; also, to play upon an
      instrument, or to act, extemporaneously.
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   2. To bring about, arrange, do, or make, immediately or on
      short notice, without previous preparation and with no
      known precedent as a guide.
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            Charles attempted to improvise a peace. --Motley.
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   3. To invent, or provide, offhand, or on the spur of the
      moment; as, he improvised a hammer out of a stone.
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