Rappelling is a popular outdoor activity that involves descending down a steep cliff or mountain using a rope. A rappeller is a person who engages in this activity, and there are several synonyms for this word. One synonym for rappeller is "abseiler," which is commonly used in the United Kingdom and Australia. Another term used for rappeller is "descender," which accurately describes the action of descending down a cliff. "Rope climber" and "cliff diver" are also used to describe someone who is rappelling. No matter what term you use, rappelling is a thrilling experience that requires skill, strength, and courage.