The legal definition is wide enough to encompass a broad range of acts that people have differing moral intuitions about (even if they are all bad acts, some are markedly more heinous in a lot of people's minds). That leads to moral vagueness. Pointing to a legal definition doesn't change that.
If I went around calling you a killer, because you kill insects, or a criminal, because you had an alcoholic drink when underage, or a producer of child pornography, because you sexted your girlfriend a photo of yourself when you were 17, and then pointed to a dictionary or legal definition to show that I was technically correct, would you not still object that I'm using terms that are overly vague as to the morality of what you have done?