The Collaborative International Dictionary of English v.0.48:

Vignette \Vi*gnette"\, v. t.
   To make, as an engraving or a photograph, with a border or
   edge insensibly fading away.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vignette \Vi*gnette"\ (?; 277), n. [F. vignette, fr. vigne a
   vine. See Vine, and cf. Vinette.]
   1. (Arch.) A running ornament consisting of leaves and
      tendrils, used in Gothic architecture.
      [1913 Webster]

   2. A decorative design, originally representing vine branches
      or tendrils, at the head of a chapter, of a manuscript or
      printed book, or in a similar position; hence, by
      extension, any small picture in a book; hence, also, as
      such pictures are often without a definite bounding line,
      any picture, as an engraving, a photograph, or the like,
      which vanishes gradually at the edge.
      [1913 Webster]

   3. A picture, illustration, or depiction in words, esp. one
      of a small or dainty kind.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

vignette
    n 1: a brief literary description [syn: sketch, vignette]
    2: a photograph whose edges shade off gradually
    3: a small illustrative sketch (as sometimes placed at the
       beginning of chapters in books)