English Computing Dictionary
◊ OB-
Ob-
/ob/ prefix Obligatory. A piece of {netiquette} acknowledging
that the author has been straying from the newsgroup's charter
topic. For example, if a posting in alt.sex is a response to
a part of someone else's posting that has nothing particularly
to do with sex, the author may append "ObSex" (or "Obsex") and
toss off a question or vignette about some unusual erotic act.
It is considered a sign of great {winnitude} when one's Obs
are more interesting than other people's whole postings.
[{Jargon File}]
 oap  oath  ob-  obdc  obe