A lexicographic error is an inaccurate entry in a dictionary. Such problems, because they undercut the intention of providing authoritative guidance to readers and writers, attract special attention.

An early English-language example was the definition of pastern as "the knee of a horse" in Dr. Johnson's famed 18th-century Dictionary of the English Language. That would suit the word fetlock, but the pastern is in fact a long portion of the leg immediately below the fetlock. Johnson is remembered for Boswell's account of him explaining the entry as "Ignorance, Madam, pure ignorance."

In the 1930s, Webster's New International Dictionary, Second Edition accidentally documented, for four years, a supposed word "dord", whose only basis was a clerical error by the publisher.