Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
will-o'-the-wisp is a noun meaning "a pale light sometimes seen at night over marshy ground". It carries 2 recorded senses.
a pale light sometimes seen at night over marshy ground
an illusion that misleads
Definitions, synonyms and semantic relations for will-o'-the-wisp come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.