From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( v. t.) To introduce with a formal preface, or prologue.

(2): ( n.) The preface or introduction to a discourse, poem, or performance; as, the prologue of Chaucer's "Canterbury Tales;" esp., a discourse or poem spoken before a dramatic performance

(3): ( n.) One who delivers a prologue.

International Standard Bible Encyclopedia [2]

prō´log , prol´og ( πρόλογος , prólogos , "foreword," "preface," "introduction"): The word occurs in the preface to Ecclesiasticus (Sirach), and is commonly applied to   John 1:1-18 . See Ecclesiasticus; John , Gospel Of .