Definition of "oligarchy"

It's an oligarchy because these families own and run almost everything that makes money in El Salvador. Coffee gave birth to the oligarchy in the late 19th century, and economic growth has revolved around them ever since.

1981 September 6, “The Eclipse of the Oligarchs”, in The New York Times‎

The Itasca Project is just one example of existing oligarchy, and a surprisingly open one at that.

2016 January 17, “Wealthy cabals run America”, in Al Jazeera America, retrieved 18 January 2016