Definition of sixty-four thousand dollar question in English:

sixty-four thousand dollar question

noun

informal
  • Something that is not known and on which a great deal depends.

    • ‘The sixty-four thousand dollar question now is what will be the Bush administration's response?’
    • ‘That has become the perennial sixty-four thousand dollar question.’

Origin

1940s: originally sixty-four dollar question, from a question posed for the top prize in a broadcast quiz show.

Pronunciation

sixty-four thousand dollar question

/ˈsɪksti fɔ(ə)r ˈθaʊznd ˈdɑlər ˈkwɛstʃən/