Meaning of JE in English

JE

ne sais quoi [noun] [U] - a pleasing quality which cannot be exactly named or describedAlthough he's not particularly attractive, he has this je ne sais quoi which makes him very popular with women.This dish seems to lack a certain je ne sais quoi - perhaps it needs a bit more spice.

Cambridge English vocab.      Кембриджский английский словарь.