To make and cause to remain secret.
To protect or preserve from.
To prevent or restrain (someone or something) from; to refrain or cause to refrain from.
To cause to be excluded or not present.
To reveal.
To undo a folding.
To release from a fold or pen.
To turn out; to happen; to develop.
To open (anything covered or closed); to lay open to view or contemplation; to bring out in all the details, or by successive development.
In functional programming, a kind of higher-order function that is the opposite of a fold.