Beating to the extreme is abuse. There are others who believe yelling at a child is abuse. There is no definitive answer. When administering corporal punishment and use an object to hit with which leaves several marks, then yes, it should be considered abuse. When a loving, functional and caring parent spanks a child with an open hand to get their attention, then discusses their behavior, I would say no, it should not be considered abuse.
People have a variety of definitions of spanking.
I define spanking as anytime you hit a child for disciplinary reasons. A parent should only spank a child with an open hand on the fleshy part of a child's bottom. Never slap a child in the face, hit them with an object or punch them with a closed fist. A parent must always be in control of themselves and their environment before ever spanking their child. A parent who is emotional should take some time to calm down and consider the different options of discipline.