1. 寡头组织；寡头统治集团；寡头统治的国家
An oligarchy is a small group of people who control and run a particular country or organization. You can also refer to a country which is governed in this way as an oligarchy .

2. 寡头政治；寡头统治
Oligarchy is a situation in which a country or organization is run by an oligarchy.

1. a political system governed by a few people

e.g. one of his cardinal convictions was that Britain was not run as a democracy but as an oligarchy
the big cities were notoriously in the hands of the oligarchy of local businessmen