ignis fatuus

noun ig·nis fat·u·us \ˈig-nəs-ˈfa-chə-wəs, -ˈfach-wəs\

plural ig·nes fat·ui \-ˌnēz-ˈfa-chə-ˌwī\

Definition of IGNIS FATUUS

: a light that sometimes appears in the night over marshy ground and is often attributable to the combustion of gas from decomposed organic matter

: a deceptive goal or hope

Medieval Latin, literally, foolish fire

First Known Use: 1563

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