What does adieu mean?
The definition of adieu
A*dieu”, interj. & adv.
Etym: [OE. also adew, adewe, adue, F. dieu, fr. L. ad to + deus God.]

Good-by; farewell; an expression of kind wishes at parting.

A*dieu”, n.; pl. Adieus.
A farewell; commendation to the care of God at parting. Shak.