snap ring vs holdfast

snap ring and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
snap ring	Yes	No	No	No
holdfast	Yes	No	No	No

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

snap ring: an oblong metal ring with a spring clip; used in mountaineering to attach a rope to a piton or to connect two ropes
holdfast: restraint that attaches to something or holds something in place

Other hypernyms of snap ring include fastener, fastening, fixing, hoop, ring, climbing equipment, rock-climbing equipment.

snap ring (noun)	holdfast (noun)
an oblong metal ring with a spring clip; used in mountaineering to attach a rope to a piton or to connect two ropes	restraint that attaches to something or holds something in place