The Collaborative International Dictionary of English v.0.48:

five-spot \five-spot\ n.
   1. (Bot.) A California annual (Nemophila maculata) having
      white flowers with a deep purple blotch on each petal.

   Syn: five spot, Nemophila maculata.
        [WordNet 1.5]

   2. a playing card or a domino or a die whose upward face
      shows five pips.
      [WordNet 1.5]

   3. A five-dollar bill. [U. S. slang]
      [PJC]

WordNet (r) 3.0 (2006):

five-spot
    n 1: a United States bill worth 5 dollars [syn: fiver, five-
         spot, five dollar bill]
    2: California annual having white flowers with a deep purple
       blotch on each petal [syn: five-spot, Nemophila maculata]
    3: a playing card or a domino or a die whose upward face shows
       five pips [syn: five-spot, five]