Contract Bridge (game)
For other uses of 'Contract Bridge' see Here
Contract Bridge is a fiendishly complex game of cards played by two teams of two, each of whom occupies a notional point of the compass. Each player is expected, without directly communicating, to be able to deduce which cards are held by the other three players, and respond accordingly. (ie, to support their team-mate and block the opposition)
The standard primer on the Disc is Nosehinger on the Laws of Contract. There is very definitely a copy in Death's Domain, as Twoflower used his copy as a teaching aid when explaining to the Four Dread Riders how the game was played: when he and Rincewind left in something of a hurry, they left the book behind.
It adds an extra dimension if played with Caroc Cards.
In The Last Continent, the Chair of Indefinite Studies suggests bridge would be a good replacement for sex as a method to propagate the species. When someone points out that bridge requires four people, he suggests croquet as an alternative.