discourtesy, disrespect - an expression of lack of respect

low blow - unscrupulous abuse

billingsgate, scurrility - foul-mouthed or obscene abuse

stinger, cut - a remark capable of wounding mentally; "the unkindest cut of all"

invective, vituperation, vitriol - abusive or venomous language used to express blame or censure or bitter deep-seated ill will