one who displays immense stupidity, and is happy to respond to the term publicly. Shitferbrains is only used in a public forum and has no value in general conversation. Typical venues for use of the word would be building sites etc - The word would be shouted loudly to gain the attention of the subject, who must respond without complaint

A person or people that purposefully causes chaos or mischief within a group for the sake of entertainment.

One who displays a lack of common sense
A fuckup

A southern term for a very dumb individual, is often used to give someone hell if they mess up on something simple.