@-party /at'par`tee/ n.
[from the @-sign in an Internet address] (alt. `@-sign party' /at'si:n par`tee/) A semi-closed party thrown for hackers at a science-fiction convention (esp. the annual World Science Fiction Convention or "Worldcon"); one must have a network address to get in, or at least be in company with someone who does. One of the most reliable opportunities for hackers to meet face to face with people who might otherwise be represented by mere phosphor dots on their screens. Compare boink.
The first recorded @-party was held at the Westercon (a U.S. western regional SF convention) over the July 4th weekend in 1980. It is not clear exactly when the canonical @-party venue shifted to the Worldcon but it had certainly become established by Constellation in 1983. Sadly, the @-party tradition has been in decline since about 1996, mainly because having an @-address no longer functions as an effective lodge pin.
We are informed, however, that rec.skydiving members have maintained a tradition of formation jumps in the shape of an @; picture at http://www.birdwalk.com/DevilsWorkshop/favorites/source/6.html.