Well, and curious as to what the words are. I've always thought it was something like "ah wa ka wa poo-say poo-say ..."
... but considering that I always thought that the chorus to "Blinded by the Light" included the amazing line "cut up like a douche, another boner in the night," I didn't want to get my hopes up. 'Scuse me while I kiss this guy.
But according to the unknown lyric source that all ten zillion lyric websites copy, the #9 Dream chorus is:
Ah! bwakawa pouss, pouss.
Ah! bwakawa pouss, pouss.
Ah! bwakawa pouss, pouss.
OK, so I wasn't that far off. But as for the meaning, that's a little trickier.
I googled the phrase and came up with 39 hits, prefaced with Google's eager suggestion:
"Did you mean: Ah! b'wakawa pouss, mouss"
Slapping my forehead, I thought: How silly of me! OF COURSE I did! Considering the proffered alternative yields ONE result, I'm a little mystified why I didn't figure that one out on my own!
The second hit on my original search was a link to Yahoo! Answers, an alternative repository of cultural trivia and information.
The "best answer chosen by voters" to someone's question as to the meaning, is "beats me."
Digging a little deeper leads me to Songfacts, which credits "Ken," in Louisville KY, for the assertion that Lennon just made it up.
I'll treat anyone who can answer this for me to a bowl of ice cream.