In "The Dead," Gabriel understands masculinity as power and potency, especially the power to command attention. Gabriel, for example, gives a speech after dinner, in which he praises “warmhearted courteous Irish hospitality.” Even in private conversation Gabriel assumes an authoritative voice and expects to be listened to, especially by the women, who he sees as lesser beings than himself. When he insults Molly Ivors by saying he is "sick" of Ireland, she leaves rather than argue with him. In his private thoughts, his potency is tied to his feelings of superiority to the other guests. Most importantly, he believes in his wife Gretta's undivided devotion.
It's therefore a shock to him him when, full of amorous feelings after the Christmas party, he finds he is not at the center of Gretta's thoughts. She is thinking instead of a former boyfriend who died, Michael Furey. As Gabriel absorbs the idea that his wife has a life apart from him, and especially an attachment to another male, Gabriel's sense of masculinity is shaken. All along, we as readers understand that he is not a potent man, but instead paralyzed: cold like the snow rather than hot like Michael Furey.
At the end of the story, having suffered a narcissistic wound, Gabriel himself comes to realize that he is not as potent as he had believed and that the world does not revolve around him. Instead, his sense of masculinity becomes less self-centered and his understanding of humanity broadens to include both the living and the dead.