get down vs dismount

get down is not a noun while dismount is a noun.

Word	Noun	Adjective	Verb	Adverb
get down	No	No	Yes	No
dismount	Yes	No	Yes	No

As verbs, get down and dismount are synonyms defined as:

Other synonyms of get down include get off, light, unhorse.

get down (noun)	dismount (noun)
	the act of dismounting (a horse or bike etc.)

get down (verb)	dismount (verb)
take the first step or steps in carrying out an action	alight from (a horse)
put down in writing; of texts, musical compositions, etc.
pass through the esophagus as part of eating or drinking
lower someone's spirits; make downhearted
move something or somebody to a lower position
alight from (a horse)
lower (one's body) as by kneeling