when does discipline turn into child abuse?

[Yvette]

now lets say you have a son that is verbaly and physicaly abusive to you as a parent. disrespects you in the grocery store by hitting you and calling you bad words. what would be your way of disciplining your child since he/she acts this way towards you and like the original question says where is the barrier between discipline and child abuse in a situation like this where your about to loose your mind over it