What is the definition of doctrine of respondeat superior?

It is a Latin term which means "Let the master speak." In legal proceedings it is the idea that employees are simply agents of the employer, and the employer is accountable for the acts of his employees. Therefore, he must explain, justify, or defend the acts, rather than the employee. Unless it is demonstrated that the employee was deliberately disregarding the directions of the employer, the employer, not the employee, will be held to account for any harm that comes as a result of the acts of the employee. In a dental setting, if a dental assistant were to injure a patient during a procedure, and the assistant and dentist were hauled into court in a lawsuit, the assistant's attorney (yes, the employee should always have their own counsel) would claim "respondeat superior". The assistant was only acting on the direction of the dentist, and therefore it is the dentist that is responsible for the injury.

While it may sound like the assistant has just thrown her boss under the bus, in legal terms, she is stating that she was not acting in an irresponsible way, and she was not free to ignore the direction of the dentist. The dentist, with his greater training and knowledge, is in a much better position to describe what happened and explain why it was not malpractice.