ignis fatuus

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ig·nis fat·u·us

 (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.

[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.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.ignis fatuus - a pale light sometimes seen at night over marshy groundignis fatuus - a pale light sometimes seen at night over marshy ground
light, 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 misleads
fancy, phantasy, illusion, fantasy - something many people believe that is false; "they have the illusion that I am very wealthy"

ignis fatuus

An erroneous perception of reality:
References in classic literature ?
What substitute can there be imagined for this ignis fatuus in finance, but that of permitting the national government to raise its own revenues by the ordinary methods of taxation authorized in every well-ordered constitution of civil government?
A personal influence is an ignis fatuus. If they say it is great, it is great; if they say it is small, it is small; you see it, and you see it not, by turns; it borrows all its size from the momentary estimation of the speakers: the Will-of-the-wisp vanishes if you go too near, vanishes if you go too far, and only blazes at one angle.
It may be only an ignis fatuus, after all, but it can do no harm to follow it with my eyes and rejoice in its lustre, as long as it does not lure me from the path I ought to keep; and I think it will not, for I have thought deeply on my aunt's advice, and I see clearly, now, the folly of throwing myself away on one that is unworthy of all the love I have to give, and incapable of responding to the best and deepest feelings of my inmost heart - so clearly, that even if I should see him again, and if he should remember me and love me still (which, alas!