rope down vs rappel

rope down is not a noun while rappel is a noun.

Word	Noun	Adjective	Verb	Adverb
rope down	No	No	Yes	No
rappel	Yes	No	Yes	No

As verbs, rope down and rappel are synonyms defined as:

Other synonyms of rope down include abseil.

rope down (noun)	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

rope down (verb)	rappel (verb)
descend by means of a rappel	descend by means of a rappel