Petroleum supermajors are sometimes collectively referred to as "Big Oil", a term used to describe the individual and collective economic power of the largest oil and gas producers, and their perceived influence on politics, particularly in the United States. Big Oil is often associated with the Energy Lobby.

Usually used to represent the industry as a whole in a pejorative or derogatory manner, "Big Oil" has come to encompass the enormous impact crude oil exerts over first-world industrial society.

http://en.wikipedia.org/wiki/Supermajor