The Wordnik Word of the Day for February 28, 2012 is

(noun) A fictitious word that has been published in a dictionary, or has been listed as genuine, as the result of misinterpretation or a typographical error.

'Ghost word' was coined by Professor Walter William Skeat in 1886. On this day in 1939, the erroneous word 'dord' was discovered in Webster's New International Dictionary, Second Edition.