hapax

/ˈhæpæks/
noun
  1. A word or phrase that appears only once in a text, corpus, or an author's work.
    • Linguists study hapaxes to learn about rare vocabulary in ancient languages.
    • The word 'honorificabilitudinitatibus' is a famous hapax in Shakespeare's plays.
    • Finding a hapax in a manuscript can help date the document.
Synonyms
What does "hapax" mean? | whatsthatwordmean | whatsthatwordmean