Well according to Dictionary.com it has something to do with "pertaining to life/existence."

When I typed it into Google, I got some kind of religious movement called "Existentialism" where "individuals create the meaning and essence of their lives, as opposed to deities or authorities creating it for them."

There is also some kind of mental condition that can be treated though "Existential therapy." The patient would usually be plagued with symptoms of worthlessness, aloneness, and some other -ness's along with mortality. Basically the person sees no real meaning/reason of their own pathetic life and suffers from a depression.

Take your pick. I don't see myself ever using this word though, unless I get some kind of psychoanalysis therapy prompt in an AP exam.

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