éminencegrise

ém·i·nence grise (ā-mē-näɴs grēzʹ) n. pl. ém·i·nence grises (ā-mē-näɴs grēzʹ)

A powerful adviser or decision-maker who operates secretly or unofficially. Also called gray eminence.

  [French, the power behind the throne : éminence, power + grise, feminine of gris, gray, shadowy.]

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