A handle, transaction ID, or other token of agreement between
cooperating programs. I give him a packet, he gives me back a
cookie.
The claim check you get from a dry-cleaning shop is a
perfect mundane example of a cookie; the only thing it's useful for is to
relate a later transaction to this one (so you get the same clothes back).
Syn. magic cookie; see also
fortune cookie. Now mainstream in the specific sense of web-browser
cookies.