will-o'-wisp

Noun

will o' the wisp (plural will o' the wisps)

1. Any of several kinds of pale, flickering light, appearing over marshland in many parts of the world with diverse folkloric explanations and multiple possible scientific explanations including bioluminescence and chemiluminescence.

   Synonyms:

   friar's lantern, ghost light, hinkypunk, ignis fatuus, jack-o'-lantern, marsh light, nightfire, Spooklight, walking fire

   1. (UK) A flickering light or lantern, especially over bogs, swamps or marshes, held by a supernatural creature who uses it to lure travelers at night to their demise.
      • They plague and annoy lazy men-servants and untidy maids with frightful dreams; oppress them as the nightmare; bite them as fleas; and scratch and tear them like cats and dogs; and often in the night frighten, in the shape of owls, thieves and lovers, or, like Will-o-the-wisps, lead them astray...1828, Thomas Keightley, The Fairy Mythology, volume I, London: William Harrison Ainsworth, page 283
2. (figuratively) A delusionary or otherwise unachievable goal that one feels compelled to pursue.
   • Some preliminary legal arrangements were made, but the scheme proceeded no further, as the various local authorities concerned were unwilling to speculate public funds on what was, even at that date, a will o' the wisp.1951 May, R. K. Kirkland, “The Cavan & Leitrim Railway”, in Railway Magazine, page 345