I assume it’s another synonym for “ass,” but you never hear the word in any context other than "out the … "
According to Frank Zappa, in the liner notes to his album The Grand Wazoo: “Anybody in any one of those lodge organizations with a stupid hat on,” said Frank, adding “actually, the guy with the biggest, dumbest hat is the Grand Wazoo.”
Hope that helps. 
It’s French for “bird.” Spelled “oiseau” in French.
Dave Barry "checked with both the Oxford English Dictionary and the Rev. Billy Graham, and they agree that the correct word is ‘wazooty.’ "
I thought it was a kazoo played through the anus. Clench your cheeks and hum!
Hm, puts a whole new spin on flipping someone the bird.
Kinda puts a different light on the lyrics to Zappa’s “Cosmik Debris”:
But he told me right then when the top popped open
There was nothin’ his box won’t do
With the oil of Aphrodite, and the dust of the Grand Wazoo
He said you might not believe this, little fella
But it’ll cure your asthma too.
Washington State University (located in Pullman, WA). WSU, pronounced “wazoo”. 
So, in other words, it’s an Asshat?
So, if I pull something from my Wazoo, I’m simply removing it from a lodge member with a stupid hat?
That doesn’t sound as fun as it should.
I believe it has many of the same characteristics as a Poobah.
Because of the fez?
The terms wazoo, kazoo, gazoo all show up in print in about the 1960’s to mean usually the anus. They have been used to mean the vagina and penis, but rather infrequently.
Where did gazoo appear in the '60s? When Ronald Reagan sarcastically told the White House press corps that (roughly) “if I answer that, you’ll just shove it up my gazoo,” several reporters credited him with coining the word. Maybe Reagan was hipper than we gave him credit for.
Because of the Poo.
Wasn’t the alien on the Flintstones the Great Gazoo?
You’re telling me!