The Collaborative International Dictionary of English v.0.48:

Au revoir \Au` re*voir"\ [F., lit., to the seeing again.]
   Good-by until we meet again.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

au revoir
    n 1: a farewell remark; "they said their good-byes" [syn:
         adieu, adios, arrivederci, auf wiedersehen, au
         revoir, bye, bye-bye, cheerio, good-by, goodby,
         good-bye, goodbye, good day, sayonara, so long]