bye-bye /baɪˈbaɪ/noun 2exclamation 1forms 1 noun2 •(informal) A goodbye. •(informal) Bedtime for a toddler, going to sleep, going to bed.Brush your teeth, it's time to go bye-bye. exclamation1 •(informal) Goodbye.Bye bye! Let's play again some time! — 1995 formsbye-byes
