Boilk is the noise you make when you wake up after being out on the piss the night before.
It's kind of like a burp except it's all wet and it consists of 99% alcohol fumes mixed with whatever fast food you scoffed like a pig on the way home, like a kebab or a battered sausage and chips.
It's better written down at the start of a blog entry. See example below
Well, that was some crazy night"