The definition presently given: Existentialism is generally defined as the group of philosophies which hold that the essence of a human is determined by its existence"  is not helpful to the reader - it is jargon - ALTERED semi-famous jargon, but jargon. This also focusses too much on Sartre. As asked BEFORE, what are some of the philosophies that belong to this "group of philosophies"?  The pronoun "its" is a poor word choice - does it refer to people or essence? Right now, it reads as saying "an essence is determined by that essences' existence". Fixing that one thing, however, does not fix  the many problems here. Also, this fails verification, since sources cited do not define existentialism this way - and changing "precedes" to "determines" is editorial synthesis. 

 If there is no general consensus then HOW  ON WHAT BASIS  is it "generally defined as" X?  The reader is owed some account of this discrepancy. Failing that, he should not be burdened with any statement about how it is "generally defined"  PARTICULARLY not when that "definition" is the ALTERED jargon of ONE author (Sartre).