nonword

/ˈnɑnˌwɜrd/
noun
  1. A string of letters that does not form a real word in a given language; often used in language tests or puzzles.
    • The puzzle asked players to find the nonword among a list of real words.
    • In the spelling test, the teacher included a few nonwords to see if students could identify them.
    • Linguists use nonwords to study how people process language.
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What does "nonword" mean? | whatsthatwordmean | whatsthatwordmean