eminence grise is a noun meaning "(French) a person who exercises power or influence in certain areas without holding an official position". It carries one recorded sense.
(French) a person who exercises power or influence in certain areas without holding an official position
“the President's wife is an eminence grise in matters of education”
French
Definitions, synonyms and semantic relations for eminence grise come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.