Sentence:  There was a good-looking Argentinian couple standing in the open flap of their tent. They were <WSD>aerialists</WSD>, checking over each other's harnesses, testing the strength of the metal grommets where the guy wires would be attached to them. 
Meaning of the word marked with <WSD> tags:  An acrobat performing high off the ground, defying a fall to earth, as on a trapeze or a tightrope.