The point at which a celebrity's behavior becomes so insane, that there is literally nothing they could do that would any longer shock or surprise you, or indeed any human being.
So named after boxer Mike Tyson, who at one time was the heavyweight boxing champion of world, since which time he has 1) married a semi-famous tv-star at the time, 2) alleged to have abused said wife, 3) divorced, 4) chewed off the ear of another boxer during a match, 5) received a facial tattoo, 6) owns and tends to his pigeon coop, located on the rooftop of a New York apartment building.
Among many other exploits. Seriously, wiki the man.
Originally coined by popular sports columnist the Sports Guy, Bill Simmons.
Bro1: Has Charlie Sheen entered the Tyson Zone?
Bro2: I'm not sure. Would you be shocked or surprised if you woke up tomorrow and read that he'd burned his own house down, and opened an alpaca farm in New Jersey?
Bro1: That would indeed not surprise me at all. Confirmed for Tyson Zone.