a farewell oration (especially one delivered during graduation exercises by an outstanding member of a graduating class)
<noun.communication>
the act of saying farewell
<noun.act>
Valediction \Val`e*dic"tion\, n. [L., valedicere, valedictum, to say farewell; vale farewell (imperative of valere to be strong or well) + dicere to say. See {Valiant}, {Diction}.] A farewell; a bidding farewell. --Donne.