Dia dúit, my irish teacher in high school back in Dublin very often when his pupils would make a mistake would splutter back to them with the word "BASTÚIN" ( the spelling??).The word always sounded like a curse(swear word) I never did find out what it meant, can someone explain what it means so I can stop laughing every time I hear or spell it. Slan go bfóill

bastún = ceann máilléid = blockhead
plural: na bastúin
vocative: A bhastúin! = You blockhead!

Not to be confused with Bostún!