What is the meaning of Existential?

1. Of or relating to existence.

   Of or relating to existence.

   Concerning the very existence of something, especially with regard to evading extinction.

   Of an assertion, etc.: assuming or suggesting the existence of something.

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

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

   Ellipsis of existential clause (“a clause that indicates the existence of something”).

   Ellipsis of existential type (“in a type system: a type that hides the underlying concrete type(s)”).

   Source: wiktionary.org