A phrase referring, in the United States, to a law that allows one to use force that would otherwise be illegal against a person that they perceive as posing an immediate threat of serious bodily harm. The name comes from the idea that one can "stand one's ground" rather than retreat. The shooter's state has a stand your ground law, so it's unlikely he'll face any charges, even though the man he shot was unarmed. It's still too early to tell whether the prosecutor will consider this a case of "stand your ground."