headfast vs mooring line

headfast and mooring line both are nouns.

Word	Noun	Adjective	Verb	Adverb
headfast	Yes	No	No	No
mooring line	Yes	No	No	No

As nouns, mooring line is a hypernym of headfast; that is, mooring line is a word with a broader meaning than headfast:

headfast: a mooring line that secures the bow of a boat or ship to a wharf
mooring line: (nautical) a line that holds an object (especially a boat) in place

Other hypernyms of headfast include mooring.

headfast (noun)	mooring line (noun)
a mooring line that secures the bow of a boat or ship to a wharf	(nautical) a line that holds an object (especially a boat) in place