Sorry. "NI3" is Webster's New International Dictionary, 3rd Edition.

I came across that abbreviation first at a venerable organization called the National Puzzlers' League
http://puzzlers.org/ (teaser: my son calls them "a bunch of the cleverest people in the world" and he doesn't dole out such praise lightly) that delights in word games and all sorts of outside-the-box verbal diversions. Might be worthwhile to glance at, particularly for any who like GEB/puzzles/etc.