Night night Definition 1 of 1Pro Tip 1/3Child-Friendly Often used with kids by caregivers as a comforting bedtime phrase. After reading a story, dad said 'night night' and tucked Jamie in. Pro Tip 2/3Casual Farewell Used informally among friends or family to say goodbye in the evening. As she left the family gathering, Ana waved saying, 'night night everyone!' Pro Tip 3/3Endearing Tone Carries a warm, affectionate feel, like a verbal hug. Grandma gave a gentle smile and whispered 'night night, sweetheart.'