Goodbye is defined as a way to express that you are leaving.
An example of goodbye is what you'd say to the hosts of a party you're leaving.
or good-bye also good-by
Used to express an acknowledgment of parting.
nounpl. good·byes or good-byes also good-bys
- An acknowledgment at parting, especially by saying “goodbye.”
- An act of parting or leave-taking: many sad goodbyes.
Origin of goodbyeAlteration (influenced by good day) of God be with you.
- An utterance of goodbye, the wishing of farewell to someone.
- John gave Rebecca a goodbye to wish her luck on her holiday.