I had a quick look at Merriam Webster’s Open Dictionary (via Library Stuff who complained that it was getting no publicity compared with Wikipedia. I have looked previously too at Wiktionary which is doing much the same thing and wasn’t too impressed, although it has probably grown since then). Anyway, among the Open Dictionary’s recent entries was:
dadaddadadadadadadadadadadadadundunnnununununnunn (noun) : theme song to star wars
dadaddadadadadadadadadadadadadundunnnununununnunn -gorge lucas, fretetereter, wrewrewrwe
Submitted by: Anonymous Dec. 18, 2005 22:30
I doubt that entry will last long, if only because I doubt it is a noun. It will probably count as an interjection or something like moo or something.