Being very angry/upset about something and then ranting about it. In extreme form: going a bit crazy.
"If that oven doesn't get fixed soon I'm going to have a spag."
"My mum had a right spag at me the other day for coming home late."
A slur that is used to insult bitchy and retarded people
Person 1: All white people are racist
Person 2: shut the fuck up you spag-ball