You can describe someone as a poseur when you think that they behave in an insincere or exaggerated way because they want to make a particular impression on other people.
[disapproval]
I am sometimes accused of being an inveterate poseur.
poseur in British English
(pəʊˈzɜː)
noun
a person who strikes an attitude or assumes a pose in order to impress others
Word origin
C19: from French, from poser to pose1
poseur in American English
(poʊˈzɜr)
noun
a person who assumes attitudes or manners merely for their effect upon others
Word origin
Fr
Examples of 'poseur' in a sentence
poseur
I was forced to face the truth that I had, for years, been denying: I was a poseur, a fraud, an artist manqué, and always would be.