million-dollar question

Alternative forms

 * $1,000,000 question
 * million dollar question

Etymology
From the TV game show , because in the last question the contestants attempt to win a top prize of $1,000,000.

Noun

 * 1)  A question that is very important or difficult to answer.

Translations

 * Dutch:
 * French: la question à un million
 * Galician: a pregunta do millón
 * German:
 * Russian: вопрос на миллион
 * Spanish: la pregunta del millón
 * Swedish: tiotusenkronorsfråga