existential

adj

1. Of or relating to existence.

   “The third univerſal is appetite; every perfect and imperfect living creature acquires ſuſtenance to eate and drink. For exiſtential or ſenſual, I grant many, that there is a Sun that ſhineth, that the fire heateth, &c. yet a blind man and the Paralytick denies both.”

   “[T]he essential cause of fiendish guilt, when it makes itself existential and peripheric— […] I find the only explanation of a moral phænomenon not very uncommon in the last moments of condemned felons—viz. the obstinate denial, not of the main guilt, which might be accounted for by ordinary motives, but of some particular act, which had been proved beyond all possibility of doubt, and attested by the criminal's own accomplices and fellow-sufferers in their last confessions: […]”

   “Most of the subjects had terminal cancer, and several died within a year after the trial—but not before having a mental adventure that appeared to have eased the existential gloom of their last days.”

2. Of or relating to existence.

   “an existential risk or threat”

   “[Karl] Jaspers' main concern has been with existential dread, which he regards not as a symptom of mental illness, but as a result of rejecting religious faith. He proposes that man's only way out of existential dread is through a "leap into faith" which reconciles man with himself and with God, and provides an experience of the absolute which transcends mere sense experience.”

   “Here, therefore, we seek to assemble and assess the evidence to provide an overview of how serious trade is as an existential threat to avian taxa in Sundaic Indonesia.”

   “To [Elon] Musk, his vast fortune is a mere side effect of his ability not just to see but to do things others cannot, in arenas where the stakes are existential.”

3. Of or relating to existence.
4. Of or relating to existentialism (“a philosophical movement emphasizing the uniqueness of each human existence in freely making its self-defining choices”).

   “Some existential thinkers are concerned with artistic expression only indirectly, that is, they are passionately interested critics and analysts of art works.”

5. Relating to part of a clause that indicates existence (for example, there is).

noun

1. (abbreviation, alt-of, ellipsis)Ellipsis of existential clause (“a clause that indicates the existence of something”).

   “In classical accounts of Finnish and Estonian grammar, the possibility of using the so-called partitive subject has been one definitional criterion for the category of existential clauses. […] We argue that existentials form a radial category, with a prototype and less canonical instances, where the prototype is clearly definable but the actual borderline between existentials and other clause types is fuzzy.”

2. (abbreviation, alt-of, ellipsis)Ellipsis of existential type (“in a type system: a type that hides the underlying concrete type(s)”).