- 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.
- Fig.: A misleading influence; a decoy.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). ignis fatuus. Retrieved September 28, 2026, from http://smartdefine.org/ignis_fatuus/definitions/2018860 |
| Chicago | Webster's. 2011. "ignis fatuus" http://smartdefine.org/ignis_fatuus/definitions/2018860 (accessed September 28, 2026). |
| Harvard | Webster's 2011, ignis fatuus, Smart Define, viewed 28 September, 2026, <http://smartdefine.org/ignis_fatuus/definitions/2018860>. |
| MLA | Webster's. "ignis fatuus" 27 May 2011. Web. 28 September 2026. <http://smartdefine.org/ignis_fatuus/definitions/2018860> |