To verbally bash a person you hate, to their face. Comes from merging the words "Loathe" and "Roasting" together. Whilst anyone can "roast" a celebrity or even a friend behind their backs, only someone who truly hates you can give you a loasting and still somehow come out looking like the good guy. A loasting does not merely take you down a peg or two. It is as if someone has taken away your shield and pissed in your face. In public. And everyone will believe, due to the righteous anger with which the loasting is delivered, that you deserve it.
We have all fantasised about giving a good loasting to the person we despise the most. Only a few, edge dwelling individuals have done so, and these loasters must be treated with respect for that which they have served.
Lesha vowed never ever to go to Tesco in the village ever again, for fear of the loasting she would inevitably receive, should she cross paths with Dee.