<jargon> To uncerimoniously disconnect someone from a system without prior warning. BBS Sysops routinely "borf" pest users by turning off the modem or by hitting the "auto-borf" key sequence.
You can also be "borfed" by software dropping carrier due to a bug.
The origin of the term is unknown but it has been in use since at least 1982.
Try this search on Wikipedia, OneLook, Google
Nearby terms: bootstrap loader « boot virus « Border Gateway Protocol « borf » Borland International, Inc. » Borland Software Corporation » BOS