lollipop man vs crossing guard

lollipop man and crossing guard both are nouns.

Word	Noun	Adjective	Verb	Adverb
lollipop man	Yes	No	No	No
crossing guard	Yes	No	No	No

As nouns, crossing guard is a hypernym of lollipop man; that is, crossing guard is a word with a broader meaning than lollipop man:

lollipop man: a man hired to help children cross a road safely near a school
crossing guard: someone who helps people (especially children) at a traffic crossing

Other hypernyms of lollipop man include adult male, man.

lollipop man (noun)	crossing guard (noun)
a man hired to help children cross a road safely near a school	someone who helps people (especially children) at a traffic crossing