The American Heritage® Dictionary of the English Language, 4th Edition
n. A market condition in which sellers are so few that the actions of any one of them will materially affect price and have a measurable impact on competitors.
n. An economic condition in which a small number of sellers exert control over the market of a commodity.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. (economics) a market in which control over the supply of a commodity is in the hands of a small number of producers and each one can influence prices and affect competitors
Word Usage
"Google has a mid term oligopoly on search aggregation."