sealing wax vs holdfast

sealing wax and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
sealing wax	Yes	No	No	No
holdfast	Yes	No	No	No

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

sealing wax: fastener consisting of a resinous composition that is plastic when warm; used for sealing documents and parcels and letters
holdfast: restraint that attaches to something or holds something in place

Other hypernyms of sealing wax include fastener, fastening, fixing.

sealing wax (noun)	holdfast (noun)
fastener consisting of a resinous composition that is plastic when warm; used for sealing documents and parcels and letters	restraint that attaches to something or holds something in place