Sentence:  Alex explained that they had been out for a stroll before breakfast while the doctor edged around behind him , attempting to hide the protuberance at his left side behind Alex 's <WSD>arm</WSD> and back . 
Meaning of the word marked with <WSD> tags:  a human limb; technically the part of the superior limb between the shoulder and the elbow but commonly used to refer to the whole superior limb