- a highly flammable composition, as Greek fire, difficult to extinguish when ignited, formerly used in warfare.
- any large fire that spreads rapidly and is hard to extinguish.
- sheet lightning, unaccompanied by thunder.
- the ignis fatuus or a similar light.
- Plant Pathology. a disease of tobacco and soybeans, characterized by brown, necrotic spots, each surrounded by a yellow band, on the leaves and caused by a bacterium, Pseudomonas tabaci.
- Pathology Obsolete. erysipelas or some similar disease.