One, who, without sufficient knowledge, study or previous preparation, and without the diploma of some college or university, undertakes to practice medicine or surgery, under the pretense that he possesses secrets in those arts. 2. He is criminally answerable for his unskillful practice, and also, civilly to his patient in certain cases. Vide Mala praxis; Physician.
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TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.