- a shifting, elusive light seen over marshes at night; will-o'-the-wisp
- a hollow pumpkin cut to look like a face and usually illuminated inside as by a candle, used as a decoration at Halloween
(plural jack o'lanterns)
- (idiomatic, English folklore) will o' the wisp, a strange light that attracts travellers
- (US, tradition) A vegetable, usually a pumpkin, but alternatively a turnip, carved into the form of a face and lighted within by a candle. Associated chiefly with the holiday Halloween.