zip vs holdfast

zip and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
zip	Yes	No	Yes	No
holdfast	Yes	No	No	No

As nouns, holdfast is a hypernym of zip; that is, holdfast is a word with a broader meaning than zip:

zip: a fastener for locking together two toothed edges by means of a sliding tab
holdfast: restraint that attaches to something or holds something in place

Other hypernyms of zip include fastener, fastening, fixing.

zip (noun)	holdfast (noun)
a fastener for locking together two toothed edges by means of a sliding tab	restraint that attaches to something or holds something in place
forceful exertion
a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential

zip (verb)	holdfast (verb)
close with a zipper
move very fast