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!
A contraction of "sun shade idiot", any person who puts their car sunshade in the front window even if the car is facing to the north (in the Northern Hemisphere- no evidence exists yet that this occurs in the Southern Hemisphere too).
Quite possibly they do it on purpose thinking that, even though it is daytime, the North Star is out there and it is bigger than the Sun. This excuse would not work in the Southern Hemisphere since they cannot see the North Star.
Contraction of the words "Social, Media & Idiot", used to describe a person who posts on social media to their detriment, in such a way as to cause themselves to be embarrassed, discredited and even potentially arrested. Plural: Smediots.