Literally it means "I do not know" in French. But it is actually an euphemism to express a pleasant or desirable trait about something or someone that can't be desribed or explained.

This French idiom is frowned upon by people who feel socially, economically, or mentally threatened because they can't stand "snobs" who use this phrase (see first definition in this list). People who fear foreign languages also have a tendency to have small reproductive organs, carry big guys to compensate for their lack of confidence, and are generally socially inept when trying to carry on an intelligent conversation with people smarter then them.
"There's a certain lack of je ne sais quoi in people who call other people snobs..."
"I don't know about that guy over there, there's definitely no je ne sais quoi in his life."
"That poor unintelligent bastard over there doesn't like people who say je ne sais quoi."
by Mr. Je ne sais quoi September 26, 2013
Get the Je ne sais quoi mug.
French: "I do not know what".

As far as english speaking people are concerned, this is spoken by snooty types as to sound more sophisticated than they are, used humorously as such by people who *do* know what it means, and spoken by French when they need to say "I don't know what" in French.

Generally speaking, can be used if you're feeling particularly suave to give an explanation of something of a certain unknown or indescribable quality.

See also unobtanium.
"This house lacks what the French may call a certain je ne sais quoi," said the pretentious rich bastard.
by ke6isf October 3, 2004
Get the Je ne sais quoi mug.
To have a certain je ne sais quoi, is to be effortlessly cool or chic without trying. It is a quality of elegance of movement and purpose, most effective and yet without apparent or visible effort, applied to any line of thought or activity. The quality makes itself visible through fashion, in the workings of one's profession, in the give-and-take of social relation, or through personal mannerisms. This quality implies lack of studied perfection - and in fact, pretense is by definition its opposite. The term 'je ne sais quoi' often refers to unstudied elegance of habit or dress, or the way in which clothing or hair naturally falls. An example from film is Johnny Depp's portrayal of Jack Sparrow - his dress, his movements, his manner of speech, combining imperfection and elegance - a certain je ne sais quoi unique to his character.a
She tossed her hair with a certain je ne sais quoi, laughing as she ascended the stairs leading to the ship's gate.
by *ThatGirlNextDoor* May 10, 2021
Get the je ne sais quoi mug.
What you say when you don't know what to say, and can't be bothered to say what you think.
You: What does "Je ne sais quoi" mean?
Me: .........Well...... Je ne sais quoi.
by Madkittykat October 7, 2010
Get the je ne sais quoi mug.