The act of going angry or mad, often when reacting to something. If someone wildy explodes with rage, they are "going sick". In the past tense, if someone went crazy or angry, they "went sick". People going sick are often laughed at, as they are probably overreacting to something and making a fool of themselves.
An expression often used in Corby, UK (therefore probably Scotland as well).
Ryan: Any of you twats touch my bike, I'm gonna go sick!
Mike: Did you see Dave? He went sick when he saw his bird getting touched up!