Definition of no you don't! in English:

no you don't!

phrase

informal
  • Used to indicate that one intends to prevent someone from doing what they were about to do.

    ‘Sharon went to get in the taxi. ‘Oh no you don't’, said Steve’
    • ‘No you don't lad. Let William and Jack go after them.’
    • ‘‘Oh no you don't!’ I shouted, jumping for the door before he could.’