jackknife clam vs clam

jackknife clam and clam both are nouns.

Word	Noun	Adjective	Verb	Adverb
jackknife clam	Yes	No	No	No
clam	Yes	No	Yes	No

As nouns, clam is a hypernym of jackknife clam; that is, clam is a word with a broader meaning than jackknife clam:

jackknife clam: marine clam having a long narrow curved thin shell
clam: burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness

jackknife clam (noun)	clam (noun)
marine clam having a long narrow curved thin shell	burrowing marine mollusk living on sand or mud; the shell closes with viselike firmness
	flesh of either hard-shell or soft-shell clams
	a piece of paper money worth one dollar

jackknife clam (verb)	clam (verb)
	gather clams, by digging in the sand by the ocean