Adicto means "addicted." While it might seem like a common word, its directness and the title of the song, "Adicto a Ti" (Addicted to You), make it incredibly impactful and central to the song's theme.
In the context of the song, Chystemc uses this word to express an intense, almost overwhelming dependency on another person. It's a strong declaration of devotion, portraying love as a powerful, all-consuming addiction, which is a compelling metaphor that draws listeners in.