Definition of what does — know? in English:

what does — know?

phrase

informal
  • Used to indicate that someone knows nothing about the subject in question.

    ‘what does he know about football, anyway?’
    • ‘He lives with his wife and daughter in a $1.9 million home in Manhattan, what does he know about the minimum wage?’
    • ‘The video seems odd to me, but it's probably the first rock video I've seen in about eight years, so what do I know?’