unfold

fe’l verb

1. To undo a folding. to unfold a map; to unfold a tablecloth; she unpacks the new dress and unfolds it carefully
2. 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
3. To release from a fold or pen. to unfold sheep
4. To turn out; to happen; to develop.

ot noun

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