ka-bunk-a-bunk - A butt that's just there, not cool, not phat, but it's there

A butt that's just there, not cool, not phat, but it's there and it’s making you mad.

That ka-bunk-a-bunk is just there, like it doesn't care about anything.

I saw my neighbor's ka-bunk-a-bunk and I just wanted to scream.

My brother's ka-bunk-a-bunk is just there, like it's mocking me.