will-o'-the-wisp; phosphorescent light
Refers to a mysterious, flickering light seen at night over marshes or graveyards, traditionally attributed to supernatural causes but scientifically explained as spontaneous combustion of marsh gases. The term is somewhat literary or folkloric.
I heard a story about seeing a will-o'-the-wisp in the graveyard at night.
燐火は科学的には自然発火現象とされる。
Will-o'-the-wisps are scientifically considered a spontaneous combustion phenomenon.