zipper vs holdfast

zipper and holdfast both are nouns.

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

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

zipper: 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 zipper include fastener, fastening, fixing.

zipper (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

zipper (verb)	holdfast (verb)
close with a zipper