noun. A ghostly critter or thingy. Maybe a ghost goat or ghost toaster. Boooooo! Hissss! I mean, booooooooooooo!
Real citation: "Yao-O-SHI-2 shouts, 'Who has that polterthing!'"
(Jan. 29, 2005, http://www.paranoia-live.net/gm_ftp/Dairun/01_29_05_Super_Mar_R_IOH_Bros.html)
Made-up citation: "I don't believe in polterthings, Zeus, Jesus, or leprechauns. But I believe in the healing power of Goldbond."