To touch a base, usually with a foot but sometimes with a hand.
To meet or make contact with someone, usually to consult, review, visit, or communicate.
To release from a fold or pen.
To undo a folding.
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.
To reveal.
In functional programming, a kind of higher-order function that is the opposite of a fold.