As used in the title of John Donne's "A Valediction: Forbidding Mourning", the word valediction is the antonym of the word B. Greeting.
A valediction is a poem of farewell (opposite to greeting), which sometimes implies a sense of presentiment or doubt about the future events. Even though the title "A Valediction Forbidding Mourning" may apparently suggest a dark, melancholic theme, John Donne's poems is in fact a love poem; an exceptional example of 16th century Metaphysical wit.