Slap, abuse?

Depends on the situation: A parent spanking their kid can be abuse or it can be a punishment because the kid did something bad.

A man or woman hitting their spouse or girlfriend/boyfriend out of anger is abuse unless one was cheating on the other or being inappropriate etc. as long as they're not hitting that person repeatedly. Men should avoid hitting a woman unless it's required for self defense.

Someone under the influence of drugs or alcohol, hitting a friend or partner is also abuse. Even if the one under the influence doesn't remember.

Few situations call for being slapped, unless the person wants to be or is doing something disrespectful or inappropriate etc.