Domestique: A road bicycle racer who works solely for the benefit of his or her team leader.
In the major races, each team leader works with eight other riders, called "domestiques," who don't have much chance of winning the race themselves. Top teams typically have 20 or more cyclists on their rosters, from which team managers can choose a nine-person team suited for each event. By tradition, the winner of a race like the Tour de France splits his cash prize with the members of the team and its staff.
What do the domestiques do? For the most part, they ride in front of the team leader. Cycling team strategy revolves around the notion that it's easier to pedal when there's someone in front of you to cut the wind. Cycling experts say that "drafting" like this can save you between 20 and 40 percent of your energy in a long event.
Domestique, the French word for "servant," is the term used in English-speaking countries. In France, however, the word for this team player is porteur d'eau--"water carrier." The German term, Wasserträger, has the same meaning. Belgium and the Netherlands use knecht (literally "knight") or helper (helper); in Italy and Spain the word is gregario (a soldier in the Roman legions; the root is the same as that in English congregate).
The most accomplished domestiques are called super-domestiques; they are called on during especially critical times in a race.
More on cycling domestiques in this Wikipedia article.