a Smithy
To do something you're not supposed to do, it’s a Smithy. It’s illegal, it’s a weak U-turn, and it’s also when you say 'Eeeeeeeeeeyeah!' like you're in a trance.
I did a Smithy by skipping class and eating all the chips in the canteen.
He did a Smithy by stealing the teacher’s coffee and then saying 'Eeeeeeeeeeyeah!' to the whole class.
She did a Smithy by cheating on her math test and then telling the teacher she was having a mental breakdown.