Vadding
Vadding is a verb which has become synonymous with urban exploration. The word comes from MIT where, for a time in the late 1970s, some of the student population was addicted to a computer game called ADVENT (also known as Colossal Cave Adventure). In an attempt to hide the game from system administrators who would delete it if found, the game file was renamed ADV. As the system administrators became aware of this, the filename was changed again, this time to the permutation VAD. The verb vad appeared, meaning to play the game. Likewise, vadders were people who spent a lot of time playing the game.
Thus, vadding and vadders began to refer to people who undertook actions in real life similar to those in the game. Since ADVENT was all about exploring underground tunnels, the MIT sport of roof and tunnel hacking became known as vadding.
Today, the word vadding is rarely used at MIT (usually only by old-timers) and roof and tunnel hacking has returned as the preferred descriptive term. Those who participate in it generally refer to it simply as "hacking".
Read more about this topic: Roof And Tunnel Hacking