- A phosphorescent light that appears, in the night, over
marshy ground, supposed to be occasioned by the decomposition of animal
or vegetable substances, or by some inflammable gas; -- popularly
called also Will-with-the-wisp, or Will-o'-the-wisp, and
Jack-with-a-lantern, or Jack-o'-lantern. - Fig.: A misleading influence; a decoy.