Bullshitter - usually male.
As you will observe, the nearest equivalent to this Greek word is in fact American. This brief term although direct, fails to capture the near-artistic nature of the true lafazanis who actually achives a level of creativity verging on the surreal at times with their Billy Liar with Münchhausen syndrome meets the pub bore performances.
The English B.S. about sexual conquests and, if old enough, what they did in the war. The lafazanis feels no such limitations and his depredations against the truth are of a general and wide ranging nature. Police officers who put judges and laywers "in their place" in court, builders who tell architects what is what with a building's design flaws, men in thiplowgambina who were demons on the Nürburgring in their youth and anyone addressing a foreigner who appears to know what they are talking about after all and so needs putting in their ignorant, foreign, compliant cash-cow place.
Confronted by Einstein in a restaurant, the true lafazani would have interrupted the scientist's meal without delay or apology to explain how the space time continuum really curved and even used the diner's knife and fork together with the contents of the salt cellar and the keys to their own potato truck to illustrate the concept so Einstein could finally understand his errors.
These flannel merchants are reasonably rare but you will know when you meet one. Do not argue with them as you will be - as the Greeks so rightly say - throwing eggs against the wall. Simply put, just walk away, Alternatively if time is not pressing, encourage them just to see how far they will take the story.
The latter option can be hilarious as the audience of canny, curious locals grows steadily and the lafazani suddenly realises that he is surrounded by people whose widening grins are the clearest possible evience that they no more believe his story than the lafazani does himself.
You may then drawl kalooooo (Literally - good. The meaning is closer to riiiiight.... though) ironically and enjoy the laughter of the crowd.