To be conspicuous but ignored or left out, especially from a group or activity. (A "rock bun" or "rock cake" is a type of hard cake with currants; what "piffy" refers to is unknown.) Primarily heard in UK. I was excited to go with my wife to her awards ceremony, but I didn't know anyone there and ended up sitting like piffy on a rock bun. After Tommy hit one of the other boys in his class, he was left sitting like piffy on a rock bun during playtime.