An essay written as a preface to a more detailed work.
[Latin prōlūsiō, prōlūsiōn-, from prōlūsus, past participle of prōlūdere, to practice beforehand : prō-, before; see pro-1 + lūdere, to play; see leid- in Indo-European roots.] pro·lu'so·ry (-sə-rē, -zə-) adj.