sleep tight!

sleep tight

Sleep well. A phrase said to someone when they are going to sleep. A: "I think I'm going to head to bed." B: "OK, sleep tight! See you in the morning." Good night, sweetheart, sleep tight!
See also: sleep, tight

sleep ˈtight!

(informal, spoken) used especially to children before they go to bed to say that you hope they sleep well: Good night, Pat, sleep tight!
See also: sleep