start up vs jump-start

start up is not a noun while jump-start is a noun.

Word	Noun	Adjective	Verb	Adverb
start up	No	No	Yes	No
jump-start	Yes	No	Yes	No

As verbs, jump-start is a hyponym of start up; that is, jump-start is a word with a more specific, narrower meaning than start up:

start up: get going or set in motion
jump-start: start (a car engine whose battery is dead) by connecting it to another car's battery

Other hyponyms of start up include kick-start, hot-wire, re-start, restart, crank, crank up, jump, jumpstart.

start up (noun)	jump-start (noun)
	starting an automobile engine that has a weak battery by means of jumper cables to another car

start up (verb)	jump-start (verb)
get off the ground	start or re-start vigorously
get going or set in motion	start (a car engine whose battery is dead) by connecting it to another car's battery