Definition of night night in English:

night night

exclamation

informal
  • Goodnight.

    ‘it's time to say night night’
    • ‘Night night all.’
    • ‘If your baby wakes or is upset, you can still go to her and simply say "night night".’
    • ‘Time for bed...night night.’
    • ‘Night night lovely people, sweet dreams.’
    • ‘Night night, Gemma, I love you.’