Hana Ali shared with the world her father's last minutes. She said that the fighter's heart kept beating for 30 minutes after his organs had shutdown.
I don't think you're technically dead if your heart is still beating. I also think if all of your organs fail then you're pretty much dead, but what do I know I'm not a doctor.
It makes for a better story if you say, Muhammad Ali was such a bad ass fighter that his heart kept beating for 30 minutes after he died. That's just legendary shit right there.