The Collaborative International Dictionary of English v.0.48:

Improvisate \Im*prov"i*sate\, a. [See Improvise.]
   Unpremeditated; impromptu; extempore. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Improvisate \Im*prov"i*sate\, v. t. & i. [imp. & p. p.
   Improvisated; p. pr. & vb. n. Improvisating.]
   To improvise; to extemporize.
   [1913 Webster]