The Collaborative International Dictionary of English v.0.48:

Pachisi \Pa*chi"si\, Parchesi \Par*che"si\, Parchisi
\Par*chi"si\, n. [Hind., fr. pachis twenty-five, the highest
   throw in the game.]
   1. A game, somewhat resembling backgammon, originating in
      India.
      [1913 Webster]

   2. A game adopted from the Indian game, using disks, as of
      pasteboard, and dice; it is played on a cross-shaped
      board. [U. S. & Eng.]
      [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

pachisi
    n 1: an ancient board game resembling backgammon; played on a
         cross-shaped board [syn: pachisi, parchesi, parchisi]