from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. will o' the wisp, a strange light that attracts travellers
- n. 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.
If you want the vapor to come out of a pumpkin, carve the jack o'lantern, then place a tall container inside with some dry ice.