A mixture of shithead and idiot. Often known for as being an insult, definately not a compliment, and NOT defined by the following person above/below/whatever, it was a common swear word my grandfather would say when driving on the road and running across a 'shidiot' who obviously didn't know what they were doing.
That stupid shidiot doesn't know how to drive! The light isn't going to get any greener, damnit!
I can't stand that asshole, he's a stupid shidiot.
A stydiot is a person who ships Stiles and Lydia on Teen Wolf. The main characteristic of a stydiot is their massive ego and extreme bitchiness. The naturalenemy of the delightful marrish shipper.
If you have to keep using the phrase Endgame , then you're a stydiot.