To inadvertently reveal any secret, particularly a secret that puts one at an advantage or disadvantage.
In card playing, to accidentally reveal one's cards or hand.
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.