gravel vs pit run

gravel and pit run both are nouns.

Word	Noun	Adjective	Verb	Adverb
gravel	Yes	No	Yes	No
pit run	Yes	No	No	No

As nouns, pit run is a hyponym of gravel; that is, pit run is a word with a more specific, narrower meaning than gravel:

Other hyponyms of gravel include ballast, bank gravel, pit-run gravel, shingle.

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

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