im·pro·vi·sa·tion /(ˌ)ɪmˌprɑvəˈzeʃən, ˌɪmprəvə ||ˌɪmprə(ˌ)vaɪ-/
  即興而作,即席演奏,即席創作
  Im·prov·i·sa·tion n.
  1. The act or art of composing and rendering music, poetry, and the like, extemporaneously; as, improvisation on the organ.
  2. That which is improvised; an impromptu.
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  improvisation
       n 1: a creation spoken or written or composed extemporaneously
            (without prior preparation)
       2: an unplanned expedient [syn: temporary expedient]
       3: a performance given extempore without planning or
          preparation [syn: extemporization, extemporisation]