US: /ˌɡʊdˈbaɪ/
UK: /ɡʊdbˈa‍ɪ/

Advanced English dictionary

exclamation, noun
used when you are leaving sb or when sb else is leaving: She didn't even say goodbye to her mother. + Say goodbye to Mary for me. + We waved them goodbye. + We've already said our goodbyes. + Kiss me goodbye! + (figurative) Take out our service contract and say goodbye to costly repair bills.
Idioms see KISS v.

Thesaurus dictionary

Farewell!, Hawaiian Aloha!; Italian Arrivederci!, Ciao!; German Auf Wiedersehen!; French Au revoir!, Adieu!; Japanese Sayonara!; Spanish ­Adios!, ­Hasta la vista!, ­Hasta luego!; Latin Vale!; Colloq Bye! or 'Bye!, Bye-bye!, Toodle-oo!, So long!, Brit Ta-ta!, Cheers!, cheerio, Old-fashioned Pip! Pip!, US See you later ( alligator)!:
We said our goodbyes and went on our way.

Concise English dictionary

+farewell, see you later
+Farewell! (expression used when parting)