Oligarchy
Etymology
From Greek oligarkhía, joining olígos ("few") with árkhein ("to rule"). The literal sense — "rule by the few" — is exactly the modern one. Aristotle used it as a technical term, contrasting rule by the few in their own interest with aristocracy, rule by the few in the common interest.
noun · /OL-ih-gar-kee/
A form of government or organization in which power rests with a small, privileged group.
What it names
It lets you see past the official label of a system to ask the real question — how few hands actually hold the levers, whatever the constitution says.
Example
Behind the republic’s elections, a handful of families ran a durable oligarchy that outlasted every change of government.
Related idea
Plutocracy narrows the claim: an oligarchy is rule by the few for any reason, while a plutocracy is rule by the few specifically because they are rich.