seatbelt vs safety belt

seatbelt and safety belt both are nouns.

Word	Noun	Adjective	Verb	Adverb
seatbelt	Yes	No	No	No
safety belt	Yes	No	No	No

As nouns, safety belt is a hypernym of seatbelt; that is, safety belt is a word with a broader meaning than seatbelt:

seatbelt: a safety belt used in a car or plane to hold you in your seat in case of an accident
safety belt: belt attaching you to some object as a restraint in order to prevent you from getting hurt

Other hypernyms of seatbelt include life belt, safety harness.

seatbelt (noun)	safety belt (noun)
a safety belt used in a car or plane to hold you in your seat in case of an accident	belt attaching you to some object as a restraint in order to prevent you from getting hurt