To repel is (1) to ward off or drive back, (2) to cause aversion or distaste, or (3) to present an opposing force. To rappel is to descend a vertical surface, especially a cliff face, by sliding down a rope with a device that provides friction. The words are easily mixed up, and the misuse of repel in place of rappel is especially common.
Then hikers leave the trail and go down a gully, rappel down a cliff, cross a creek and hike another 150 meters to get to the base of the climb. [Cody Enterprise]
There is no amount of money you could pay us to rappel off of a giant glass building. [Westword]
Commander of Iran’s Army Major General Ataollah Salehi says the army will powerfully repel any possible attack against the country’s sovereignty. [Press TV]
Gottlieb said boy-oriented packaging, even if the customer soon discards it, carries an enduring message that may repel girls. [Monsters and Critics]