"The Dead" is about the way the dead haunt the living. The title reflects the theme of the story.
Gabriel feels haunted in general by the Irish past and his inability to escape it. More significantly, at the end of the story he has to face the way the past specifically intersects with his own personal life. After a Christmas party, he is alone in a hotel with his wife, Gretta. He is feeling amorous, but she is disinterested. When he asks what is on her mind, she tells him she is thinking of her former love, Michael Furey, who died at seventeen. Gabriel is shocked and hurt that she ever loved someone else: he had never known before about this dead young man who has suddenly intruded into his life.
Looking out the window, Gabriel watches the snow fall and ponders death, knowing that someday he too will die. As the story comes to its conclusion, the final note falls on the word "dead," emphasizing the theme:
His soul swooned slowly as he heard the snow falling faintly through the universe and faintly falling, like the descent of their last end, upon all the living and the dead.
James Joyce's story "The Dead" exists as one piece of a greater whole. The story is the final text found within Joyce's collective work named Dubliners. As the final story, it speaks to the collections resounding theme of Irish nationality and paralysis of its people (in regards to mobility and spirituality). Essentially, the tales (as a whole) denoted the Dubliners' (inhabitants of Dublin, Ireland) inability to live life to its fullest extent.
As for the text itself, the title refers to both literal death (as seen through Joyce's use of deceased friends and family) and spiritual death (as seen in the character Conroy and his lack of spiritual growth). Given the text is filled with references to things past (emotion, love, feeling, and spirituality), the title serves as a proper denotation and connotation of the word "dead."