adieu(n = noun.communication) adios, arrivederci, au revoir, auf wiedersehen, bye, bye-bye, cheerio, good day, good-by, good-bye, goodby, goodbye, sayonara, so long - a farewell remark; "they said their good-byes"
is a kind of farewell, word of farewell

   Good-by; farewell; an expression of kind wishes at parting. [1913 Webster]

   A farewell; commendation to the care of God at parting. Shak. [1913 Webster]

adieu, int. & n.
--int. goodbye.
--n. (pl. adieus or adieux) a goodbye.

Etymology:
ME f. OF f. {agrave} to + Dieu God

N  departure, decession, decampment, embarkation, outset, start, removal, exit, exodus, hejira, flight, leave taking, valediction, adieu, farewell, goodbye, auf wiedersehen, sayonara, dosvidanya, ciao, aloha, hasta la vista, stirrup cup, valedictorian, starting point, starting post, point of departure, point of embarkation, place of departure, place of embarkation, port of embarkation, airport, take-off point, taxiing runway, runway, launching pad, spaceport, departing, valedictory, outward bound, whence, hence, thence, with a foot in the stirrup, on the wing, on the move, Int, begone!, farewell!, adieu!, goodbye!, good day!, au revoir!, fare you well!, God bless you!, God speed!, all aboard!, auf wiedersehen!, au plaisir de vous revoir!, bon voyage!, gluckliche Reise!, vive valeque!.