Quack
Quack was a derogatory term for a medical doctor who was believed to be acting fraudulently in their practice of medicine.

In 2371, Quark called Julian Bashir a quack after his examination of Grand Nagus Zek failed to find any medical problems which might alter his behavior. Quark believed such a result was not in keeping with Bashir's reputation, which was enhanced by a nomination for a Carrington Award, of being one of the best doctors in the Federation. ()

See also
Snake oil salesman
Swindler

External link
 

Insults
Medical occupations
Illegal occupations