noun

1. A farewell, a goodbye; especially a fond farewell, or a lasting or permanent farewell.

   “We bid our final adieus to our family, then boarded the ship, bound for America.”

interjection

1. Said to wish a final farewell; goodbye.

Synonyms: addio, adios, aloha, arrivederci, au revoir, auf Wiedersehen, bye, bye-bye