Merriam-Webster Collegiate Dictionary - farewell

 I. verb imperative  Date: 14th century get along well — used interjectionally to or by one departing  II. noun  Date: 14th century  1. a wish of well-being at parting ; good-bye  2.  a. an act of departure ; leave-taking  b. a formal occasion honoring a person about to leave or retire  III. transitive verb  Date: 1580 chiefly Australian & New Zealand to bid ~ to  IV. adjective  Date: 1669 of or relating to leave-taking ; final a ~ performance