Seems strange to me that "onomatopoeia" is one of the least onomatopoetic words in the English language. How about this:
<pre><font class="small">code:</font><hr>
noun: zoomwhizbuzz
plural: zoomwhizbuzzes
verb (reg): zoomwhizbuzz
adjective: zoomwhizbuzzish
adverb: zoomwhizbuzzly
interjection: zoomwhizbuzzt!
</pre><hr>