A ghost word is a word published in a dictionary or similarly authoritative reference work, having rarely, if ever, been used in practice, and hitherto having been meaningless (for example "abacot" or "kime"). As a rule a ghost word will have originated from an error, such as a misinterpretation, mispronunciation, misreading, or from typographical or linguistic confusion.

More information and some examples on the Wikipedia page [1] and the article on Dord [2].