A word (as NATO, radar, or snafu) formed from the initial letter or letters of each of the successive parts or major parts of a compound term are considered an Acronym. As some of you may recall I had some discussions around this a while back via my comments on this post http://blogs.msdn.com/mscrmfreak/archive/2006/03/12/today-s-word-rss.aspx and this one http://blogs.msdn.com/mscrmfreak/archive/2006/03/13/550053.aspx
Often it is really hard for me to follow discussions or understand what they are talking about in emails as I am not a native English speaker. A while ago I bumped into the website http://www.acronymfinder.com and was amazed by how much acronyms they have in their database. It contains more than 575,000 human-edited entries and Acronym Finder is the world's largest and most comprehensive dictionary of acronyms, abbreviations, and initialisms.
Just as an example, click here to get the possible answers for RSS!