In insider jargon among fireworks professionals a "birthday cake" or more briefly just a "cake" is a firework technically referred to as a "multi-shot tube device." These are fireworks that consist of multiple, usually small mortar tubes bundled together designed to fire a series of low-level aerial effects. The effects might be stars, comets, whistles, salutes, etc.
"Let's set those birthdaycakes up over on the left of the firing line."
When its a Facebook 'friends' birthday and like everyone else you write happy birthday on their wall, but you wait until later that day so they can see it and it wont be buried under all the other comments.
Oh look its jacks Birthday!
I know.
Aren't you gonna say something?
Yeah but I'll do the Birthday wait so he can actually see it.
Oh...
This is when you smoke a joint by sticking the unlit end into the hole in the bowl of a pipe. It is so called because the joint looks like a birthday candle. You can burn a whole doob down to the ash like this. You can also fill the bowl with weed around the joint and get really crazy.
"This joint is getting to short to hold. Stick it in my pipe and we'll have a lil birthdaybowl."