Colloquially it means “your blood is free” to other people. It gives islamic religious lunatics a reason to kill you. If you are somewhat of a known person you should be worried. In a regular legal system (as in not in an islamic sharia law place) this can pass as a threat and legal action should be taken against the one who said it to you.
What im saying is the popular street meaning of this and thus it shouldn’t be taken lightly. Its a threat. Period full stop.
Theologically it just means some religious legal entity ruled against you in your absence.