I can't bring myself to use the word abuse in relation to a measured form of punishment (like a smack on the hand etc), it just doesn't sit right with me to be honest, to compare it with actual child abuse, where there is no cause and effect or teaching moment, child abuse is simply because an adult enjoys causing harm and fear to a smaller weaker being, they enjoy the power the hold over them.
My personal opinion is that the two are really far removed from each other, and can't be compared, but there will always be people on here who can't seem to see (or won't admit) that there is a massive difference between the two things, and to insist they are the same is very narrow minded IMO.
I think the problem is a lot of instances of parents hitting their kids is because they themselves are angry or frustrated and they lash out in the moment as a way to release that tension, IMO that's very wrong and teaches absolutely nothing, but as much as I wholly disagree with it, as a one off in response to a fraught situation, like in OPs case, I struggle to see it as abuse too if I'm being perfectly honest.
Abuse to me is unprovoked and unwarranted and prolonged, there is no cause and effect, the victim will have done absolutely nothing intentional to cause it, in fact they often go out of their way to avoid it, but the perpetrator of the abuse does it anyway because they want to feel more powerful over a smaller/weaker person, and they know they can achieve that through physical harm or the threat of physical harm.