Ignis Fatuus

Part of speech: noun (n.)

1. A phosphorescent light that appears, in the night, over marshy ground, supposed to be occasioned by the decomposition of animal or vegetable substances, or by some inflammable gas; -- popularly called also Will-with-the-wisp, or Will-o'-the-wisp, and Jack-with-a- lantern, or Jack-o'-lantern.

2. Fig.: A misleading influence; a decoy. Scared and guided by the ignis fatuus of popular superstition. Jer. Taylor.