Dord is a notable error in lexicography, an accidental creation, or ghost word, of the G. and C. Merriam Company's staff included in the second (1934) edition of its New International Dictionary, in which the term is defined as "density".
Philip Babcock Gove, an editor at Merriam-Webster who became editor-in-chief of Webster's Third New International Dictionary, wrote a letter to the journal American Speech, fifteen years after the error was caught, in which he explained why "dord" was included in that dictionary.
On July 31, 1931, Austin M. Patterson, Webster's chemistry editor, sent in a slip reading "D or d, cont./density." This was intended to add "density" to the existing list of words that the letter "D" can abbreviate. The slip somehow went astray, and the phrase "D or d" was misinterpreted as a single, run-together word: Dord. (This was a plausible mistake because headwords on slips were typed with spaces between the letters, making "D or d" look very much like "D o r d".) A new slip was prepared for the printer and a part of speech assigned along with a pronunciation. The would-be word got past proofreaders and appeared on page 771 of the dictionary around 1934.
On February 28, 1939, an editor noticed "dord" lacked an etymology and investigated. Soon an order was sent to the printer marked "plate change/imperative/urgent". In 1940, bound books began appearing without the ghost word but with a new abbreviation (although inspection of printed copies well into the 1940s show "dord" still present). The non-word "dord" was excised, and the definition of the adjacent entry "Doré furnace" was expanded from "A furnace for refining dore bullion" to "a furnace in which dore bullion is refined" to close up the space. Gove wrote that this was "probably too bad, for why shouldn't dord mean 'density'?" The entry "dord" was not removed until 1947.
- Fictitious entry
- Frindle, a children's novel in which a fictitious word passes into common parlance
- Boole's rule, a mathematical rule of integration sometimes known as Bode's rule, due to a typo in Abramowitz and Stegun (1972, p. 886) that was subsequently propagated 
- Philip Babcock Gove. "The History of 'Dord'". American Speech. Volume 29 (1954). Pages 136-138.
- William Allan Neilson and others. Webster's New International Dictionary, Second Edition. G. & C. Merriam Company, 1943.
- "Ghost Word" with Emily Brewster, part of the "Ask the Editor" series at Merriam-Webster.com
- Weisstein, Eric W., "Boole's Rule", MathWorld.