Mountweazel: Any made-up word included in a dictionary or other reference book as a copyright trap.
"Mountweazel" got its name from a fake entry in the 1975 edition of the New Columbia Encyclopedia. According to a 2005 New Yorker article on copyright traps, Lillian Virginia Mountweazel was purported to be:
a fountain designer turned photographer who was celebrated for a collection of photographs of rural American mailboxes titled “Flags Up!” Mountweazel, the encyclopedia indicates, was born in Bangs, Ohio, in 1942, only to die “at 31 in an explosion while on assignment for Combustibles magazine.”
In the second edition of the New Oxford American Dictionary, the mountweazel is esquivalience, whose fake definition is "the willful avoidance of one's official responsibilities." Erin McKean, editor-in-chief of that dictionary,
said that Oxford had included it in NOAD’s first edition, in 2001, to protect the copyright of the electronic version of the text that accompanied most copies of the book. “The editors figured, We’re all working really hard, so let’s put in a word that means ‘working really hard.’ Nothing materialized, so they thought, Let’s do the opposite.” An editor named Christine Lindberg came up with “esquivalience.” The word has since been spotted on Dictionary.com, which cites Webster’s New Millennium as its source. “It’s interesting for us that we can see their methodology,” McKean said. “Or lack thereof. It’s like tagging and releasing giant turtles.”
A similar tradition of deliberate falsifying exists, for the same reason, in mapmaking. "Map traps" are sometimes called "bunnies" (after the find-the-hidden-bunny drawings popular in the 1930s) or simply "hooks." Read more about map traps here (and be sure to read the comments).