There is. Many people use it. Have you ever gone out of your way to examine it? Or do you just infer it based on your internal beliefs and limited experiences?
There's no need to assume that anyone that questions it hasn't had experiences regarding it. Just the fact that there exists in your response any implication that a lack of experience may change someone's definition of "hate speech" makes it amorphous. There may be a definition, but it being "clear" is questionable. Obviously the answer is to leave it to the courts, but then you have to consider the definitions of "attack" or "intimidate" or "discomfort" and if any amount of these is "violence" and to what extent is it punishable.