Definition of "ignis fatuus" []

• 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. (noun)
• Something that misleads or deludes; an illusion. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "And yet they say that the ignis fatuus (as it is called), which sometimes even settles on a wall, has not much heat, perhaps as much as the flame of spirit of wine, which is mild and soft."
• "When thou rannest up Gadshill in the night to catch my horse, if I did not think thou hadst been an ignis fatuus or a ball of wildfire, there's no purchase in money."
• "It appears, however, that of all flame that of spirit of wine is the softest, unless perhaps ignis fatuus be softer, and the flames or sparklings arising from the sweat of animals."