bank gravel vs gravel

bank gravel and gravel both are nouns.

Word	Noun	Adjective	Verb	Adverb
bank gravel	Yes	No	No	No
gravel	Yes	No	Yes	No

As nouns, gravel is a hypernym of bank gravel; that is, gravel is a word with a broader meaning than bank gravel:

Other hypernyms of bank gravel include crushed rock.

bank gravel (noun)	gravel (noun)
gravel as found in natural deposits	rock fragments and pebbles

bank gravel (verb)	gravel (verb)
	be a mystery or bewildering to
	cover with gravel
	cause annoyance in; disturb, especially by minor irritations