fig.: a misleading influence; a decoy.
2. ignis fatuus ·- 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.