Mc Shit is where you go to mac donalds and mc nuggets and mc chip and fucken mc big mac and the go to the toilet and chuck a big shit in the toilet without flushing it and leaving it to stink out the whole place
When you go to McDonald's and ask for a McGangbang and it pisses off the cashier so he shits on your burgers and makes you put them together yourself.
Customer: "Can I have 1 McGangbang please?"
Cashier: "WTF thats not on the menu!"
Customer: "Fine I'll make it myself!"
Cashier: *Makes burgers and shits in them aka Mc Shithead*
Cashier: "Here you go asshole!"
Customer: *Takes a bite of shit*
Customer: "FUUUUUUUUUUUUUUUUUUUU-"
an exclamation of both suprise , and of something mildy bad that just happened. like when you eat a mcdonalds, and then you fart, but oops, it was more than just a fart.
or really....just saying this to be cute or funny, or to use a cuss exclamation m and soften it by being a bit cutsie, instead of just rankly saying "shit!"