(OT) A complete reimplementation of all levels of the Macintosh networking code including "Classic" AppleTalk and MacTCP. It appeared in MacOS revision 7.5.3 [or earlier? Date?].
Last updated: 2000-08-13
Open Trading Protocol ♦ OpenTransport ♦ Open University ♦ OpenVMS
Try this search on Wikipedia, Wiktionary, Google, OneLook.