light up vs spotlight

light up is not a noun while spotlight is a noun.

Word	Noun	Adjective	Verb	Adverb
light up	No	No	Yes	No
spotlight	Yes	No	Yes	No

As verbs, spotlight is a hyponym of light up; that is, spotlight is a word with a more specific, narrower meaning than light up:

Other hyponyms of light up include floodlight.

light up (noun)	spotlight (noun)
	a lamp that produces a strong beam of light to illuminate a restricted area; used to focus attention of a stage performer
	a focus of public attention

light up (verb)	spotlight (verb)
introduce light into	illuminate with a spotlight, as in the theater
begin to smoke	move into the foreground to make more visible or prominent
become clear
start to burn with a bright flame
ignite