From Blaseball Wiki

Death is a state of being first proposed in Theoretical Blaseball Physics in which a player ceases to live while some portion of their corporeal existence, at least temporarily, remains. Not to be confused with Annihilation, or Relegation, Death was first discovered to potentially exist within current formulations of the Blaseball Standard Model in XX15. Many Blaseball physicists consider the concept of Death to be observationally validated by the existence of Incineration, which displays many of the properties long theorized to be associated with Death. Others, however, maintain that Incineration does not actually cause the cessation of life and is therefore merely a form of temporary suspension, while others believe it is a particularly energetic form of Annihilation.