charlatan

A mountebank, someone who addresses crowds in the street; (especially), an itinerant seller of medicines or drugs.

The poor foreigner, more dead than alive, answered that he was an Italian charlatan, who had practised with some reputation in Padua […].

A malicious trickster; a fake person, especially one who deceives for personal profit.

“If there’s something you don’t understand,” urged Dr. Breed, “ask Dr. Horvath to explain it. He’s very good at explaining.” He turned to me. “Dr. Hoenikker used to say that any scientist who couldn’t explain to an eight-year-old what he was doing was a charlatan.” “Then I’m dumber than an eight-year-old,” Miss Pefko mourned. “I don’t even know what a charlatan is.”

That this disgraceful charlatan holds one of the great offices of state in this country should be a source of constant shame and embarrassment to the Prime Minister.