Spud

No, this is not used as another name for a Potato but rather, in this case, a way of calling someone an idiot. It is used as an insult to someone when they make a dumb and small mistake.
Can, and will often, be used in it's adjective form 'spuddy'
Synonyms for spud: Spesh, idiot or muppet
Synonyms for spuddy: Daft, stupid, retarded (if you're a year 7 who just learnt what it feels like to nut) or special

Oh my god Adam, you spuddy kid.
How did you get that wrong you absolute spud.