Other forms: valedictories; valedictorily
A valedictory is a speech expressing farewell, as at a school graduation. The adjective valedictory relates to saying good-bye, but almost always refers to a speech or address.
Many people think of a valedictory address as the graduation speech given by the kid who got the highest grades in school — and often it is — but valedictory words don't have to have anything to do with schools or grades or throwing your cap in the air. They're all about taking one's leave or saying farewell, whether it's the president leaving office or a worker reaching retirement or a friend at a going-away party.