Final answer:
The prone position refers to lying flat on the stomach with the front of the body touching the surface. This position is used during physical examinations or medical treatments.
Step-by-step explanation:
When a resident is lying flat on his stomach, he is in the prone position. In the prone position, the person is facing downward with the front of their body touching the surface they are lying on. This position is commonly used during physical examinations or when receiving certain medical treatments.