( often initial capital letter ) Greek History .

any of a class of professional teachers in ancient Greece who gave instruction in various fields, as in general culture, rhetoric, politics, or disputation.

a person belonging to this class at a later period who, while professing to teach skill in reasoning, concerned himself with ingenuity and specious effectiveness rather than soundness of argument.

a person who reasons adroitly and speciously rather than soundly.

a philosopher.