rappel / repel are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
rappel: (noun) (mountaineering) a descent of a vertical cliff or wall made by using a doubled rope that is fixed to a higher point and wrapped around the body. (verb) lower oneself with a rope coiled around the body from a mountainside.
repel: (verb) cause to move back by force or influence. (verb) be repellent to; cause aversion in. (verb) force or drive back.
rappel: NA
repel: r·ih·p·EH·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)