Buile describes a state of divinely or supernaturally induced madness that transforms its subject into a wild, visionary figure living outside the boundaries of ordinary society. In Buile Shuibhne, the Ulster king Sweeney is driven mad by a cleric's curse and spends years as a wild man of the woods, composing lyric nature poetry of extraordinary beauty from the trees where he perches. The tale became a central text for modern Irish and Ulster poets: Seamus Heaney translated it as Sweeney Astray, and the figure of the mad poet-wanderer became a powerful archetype for the artist alienated from society but intensely alive to the natural world.

Buile describes a state of frenzied madness or rage, often induced by supernatural forces or extreme emotional trauma. In early Irish literature, it is associated with warriors like Cú Chulainn or poets like Suibhne Geilt, who gain extraordinary powers but lose their sanity. Poets use buile to explore the thin line between inspiration and insanity, suggesting that true poetic vision requires a departure from normal rationality. It is a powerful metaphor for the destructive potential of unchecked emotion or divine possession.