an essay of an introductory nature, preliminary to a more profound work.
Origin: 1595–1605; < Latin prōlūsiōn- (stem of prōlūsiō) preliminary exercise, prelude, equivalent to prōlūs(us), past participle of prōlūdere (prō-pro-1 + lūdere to play; compare prelude) + -iōn--ion