jack-o’-lantern

noun

1. a hollowed pumpkin with openings cut to represent human eyes, nose, and mouth and in which a candle or other light may be placed, traditionally made for display at Halloween.
2. a commercially made lantern resembling this.
3. any phenomenon of light, as a corona discharge or an ignis fatuus.
4. a poisonous luminescent orange fungus, Omphalotus olearius, often found in clusters at the base of hardwood tree stumps.

noun

1. a lantern made from a hollowed pumpkin, which has holes cut in it to represent a human face
2. a will-o’-the-wisp or similar phenomenon