The Collaborative International Dictionary of English v.0.48:

Tiffin \Tif"fin\, n. [Properly, tiffing a quaffing, a drinking.
   See Tiff, n.]
   A lunch, or slight repast between breakfast and dinner; --
   originally, a Provincial English word, but introduced into
   India, and brought back to England in a special sense.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tiffin
    n 1: a midday meal [syn: lunch, luncheon, tiffin,
         dejeuner]