A lack of care that shows reckless disregard for the safety or lives of others; conduct so extreme that it appears to be a conscious violation of other people's right to safety.
In personal injury law, gross negligence rises far above ordinary negligence (the legal standard used to establish liability in most injury cases); when it results in injury, gross negligence can affect the amount of compensable losses ("damages" in the language of the law).
A few examples might help illustrate the difference between ordinary negligence and gross negligence: