In Swiss legal terms, a person is said to be acting in gross negligence when they neglect basic security rules which a more sensible person would presumably have followed in order to avoid possible hazards.
When you make a claim, your insurance company may cut benefits if the covered hazards are caused by gross negligence.
Example: You light a candle in your living room and then go to the kitchen. The candle falls onto the carpet and the fire spreads from there unnoticed, because nobody is in the living room.
Because insurance regulations require that candles be used under supervision, this would be considered a case of gross negligence. Your household insurer would not be obligated to pay the (full) cost of damages.
Swiss household insurance compared