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From Middle English unfolden, from Old English unfealdan (to unfold), equivalent to un- +‎ fold.


unfold (third-person singular simple present unfolds, present participle unfolding, simple past and past participle unfolded)

  1. To undo a folding.
    • Herbert
      Unfold thy forehead gathered into frowns.
    to unfold a map; to unfold a tablecloth; she unpacks the new dress and unfolds it carefully
  2. (intransitive) To turn out; to happen; to develop.
    • 2012 November 8, Scott Tobias, “Memento’s puzzle structure hides big twists and bigger profundities”, in The AV Club[2]:
  3. (transitive) To reveal.
  4. To open (anything covered or closed); to lay open to view or contemplation; to bring out in all the details, or by successive development.
    to unfold one's designs;  to unfold the principles of a science
  5. To release from a fold or pen.
    to unfold sheep




unfold (plural unfolds)

  1. (computing, programming) In functional programming, a kind of higher-order function that is the opposite of a fold.