An expression of disgust, usually accompanied with a wrinkle of the nose, expressed by young girls (and boys) who attend private schools, and also old-ish women (and men) who associate with children of the age of 5 and below.
Tends to make international people double up in laughter.
Avanti: i want that bag!
Tash: POOOOOOOOOOOOOOOO its SOOO CHAVVYYYYYYYYY.
poopoooo, u chaaavvvvvvv.
Avanti looks bemused.