If you have a copy of the New Oxford American Dictionary, please disregard the entry for esquivalience, which is supposedly the wilful avoidance of one’s official responsibilities or the shirking of duties. It has been discovered to be a fake entry.
Compilers of reference works sometimes include them to reveal copyright infringements by competitors. Map makers might include a fictitious location, for example, or the compilers of wine encyclopaedias add entries for non-existent beverages (such as that for Via Gra in one of Robert Parker’s recent wine guides). The 1980 edition of the New Grove Dictionary of Music had a spoof entry for the composer Esrum-Hellerup. Since nobody consulting such works would ever have cause to look them up, they do no harm (unless you’re one of that vanishingly rare breed that reads such works cover to cover and commits the whole to memory).
Since we have no English word for deliberately invalid entries, some academics have used the German Nihilartikel. This is formed from the Latin nihil, nothing, plus German Artikel, so “nothing article”. In the past, we weren’t sure whether this was a real German word or one that had been invented as a joke by some English writer. However, half a dozen appearances in German sources since 2000, more than in English, suggest that it is a real, albeit rare, native German word. The first so far found is this:
Dass jedes Lexikon im Fachjargon „Nihilartikel” genannte Stichwörter enthält.
[That every dictionary contains terms which are called “Nihilartikel” in technical jargon.]
Der Orthodidakt by Katharina Hein, in the Berliner Morgenpost, 16 Jul. 2000.
This is another example:
Der Artikel „Apopudobalia” is schon jetzt berühmt: er suggestiert, es habe in der Antike eine Vorfall des Fußballs gegeben. Er gehört in die Tradition der sog. Nemo- oder Nihilartikel: dabei werden erfundene Artiken oder Fußnoten in ernste Werke eingeschleust.
[The article on “apopudobalia” is already famous: it suggests that a precursor of football existed in antiquity. It belongs in the tradition of the so-called Nemo- or Nihilartikel, in which invented articles or footnotes were smuggled into serious works.]
Das Studium der Kunstgeschichte, by Rente Prochno, 2003. Nemo is another Latin word, meaning “nobody”, so Nemoartikel is presumably a false article about a person.
The word has made only very rare appearances in non-specialist English-language works. This is one of them:
There is considerable distrust among the community that the PostZon database is “clean” — that is, contains no intentionally wrong entries that Royal Mail could use to identify unlicensed use. Such an intentional mistake — known as a Mountweazel or Nihilartikel — effectively poisons the database to unlicensed users, because its presence proves that the data was copied rather than created from scratch.
Guardian, 24 Sep. 2009.
The other term in this quotation, Mountweazel, derives from the fake entry for Lillian Virginia Mountweazel that was inserted by its editors into the 1975 edition of the New Columbia Encyclopedia. The article claimed that she was a fountain designer turned photographer, celebrated for a collection of photographs of rural American mailboxes titled Flags Up!
A much older example of a Nihilartikel (or just possibly a skittish jest) formed the final entry in several editions of Rupert Hughes’ The Music Lovers’ Encyclopedia, first published in 1903; it asserted that zzxjoanw was the name of a Maori drum. I know at least two popular works on etymology that cite the word in all seriousness, despite the fact that there’s no Z, X or J in the Maori language and that it was exposed as a fake in 1976.
Another term sometimes employed is ghost word, though this strictly refers to one which appears in a dictionary through an editorial or printer’s error, such as the entry for dord in Webster’s New International Dictionary in 1934, a misprint for D or d, as an abbreviation for “density”.