In certain social groups, it's come to mean "to kill violenty". Typically by means of strangulation. It can also mean being shot from time to time but the latter is it's more common use. Either way, to be 'gacked' means to be killed violently and or by surprise. But strangely, is almost always used in jest or a playful nature.
by WeeLilFaggot February 27, 2020