an elaborately staged activity, performance, presentation, or event designed to sway or convince people (from a derisive term for a small circus)

A demonstration or proof of concept (often done for a client) to prove the product works as sold or to show how a design on paper looks once actually built. May or may not be a waste of time. Used in the special effects industry among many others.

Pretending to be something you're not or doing something that you want people to think is important when it really isn't.

A term used to describe a more useless than tits-on-a-bull project that your useless fuck of an employer has you working on. And when it blows up in their face, they are asking why you didn't work hard enough.

working to hard for something that aint worth shit

when you get to a bar or club, and there is a line of yuppies down the block, and big black bouncers that won't let anyone in, and you have to piss so badly your bladder is going to rupture.