ignis fatuus

ig·nis fat·u·us

I0026600 (ĭg′nĭs făch′o͞o-əs)n. pl. ig·nes fat·u·i (ĭg′nēz făch′o͞o-ī′) 1. A phosphorescent light that hovers or flits over swampy ground at night, possibly caused by spontaneous combustion of gases emitted by rotting organic matter. Also called friar's lantern, jack-o'-lantern, will-o'-the-wisp, wisp.2. Something that misleads or deludes; an illusion.

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[Medieval Latin : Latin ignis, fire + Latin fatuus, foolish.]

ignis fatuus

(ˈɪɡnɪs ˈfætjʊəs) n, pl ignes fatui (ˈɪɡniːz ˈfætjʊˌaɪ) another name for will-o'-the-wisp[C16: from Medieval Latin, literally: foolish fire]

ig•nis fat•u•us

(ˈɪg nɪs ˈfætʃ u əs)

n., pl. ig•nes fat•u•i (ˈɪg niz ˈfætʃ uˌaɪ) 1. Also called will-o'-the-wisp. a flickering phosphorescent light seen at night chiefly over marshy ground and believed to be due to spontaneous combustion of gas from decomposed organic matter. 2. something deluding or misleading. [1555–65; < Medieval Latin: literally, foolish fire]

ignis fatuus

A Latin phrase meaning foolish fire, used to mean a naturally produced phosphorescent light sometimes seen over swampy land at night.

Thesaurus

Noun	1.	ignis fatuus - a pale light sometimes seen at night over marshy groundfriar's lantern, jack-o'-lantern, will-o'-the-wisplight, visible light, visible radiation - (physics) electromagnetic radiation that can produce a visual sensation; "the light was filtered through a soft glass window"
	2.	ignis fatuus - an illusion that misleadswill-o'-the-wispfancy, phantasy, illusion, fantasy - something many people believe that is false; "they have the illusion that I am very wealthy"

ignis fatuus

nounAn erroneous perception of reality:delusion, hallucination, illusion, mirage, phantasm, phantasma, will-o'-the-wisp.