concrete jungle vs jungle

concrete jungle and jungle both are nouns.

Word	Noun	Adjective	Verb	Adverb
concrete jungle	Yes	No	No	No
jungle	Yes	No	No	No

As nouns, jungle is a hypernym of concrete jungle; that is, jungle is a word with a broader meaning than concrete jungle:

concrete jungle: an area in a city with large modern buildings that is perceived as dangerous and unpleasant
jungle: a location marked by an intense competition and struggle for survival

concrete jungle (noun)	jungle (noun)
an area in a city with large modern buildings that is perceived as dangerous and unpleasant	a place where hoboes camp
	an impenetrable equatorial forest
	a location marked by an intense competition and struggle for survival