air cushion vs shock absorber

air cushion and shock absorber both are nouns.

Word	Noun	Adjective	Verb	Adverb
air cushion	Yes	No	No	No
shock absorber	Yes	No	No	No

As nouns, shock absorber is a hypernym of air cushion; that is, shock absorber is a word with a broader meaning than air cushion:

air cushion: a mechanical device using confined air to absorb the shock of motion
shock absorber: a mechanical damper; absorbs energy of sudden impulses

Other hypernyms of air cushion include cushion, shock.

air cushion (noun)	shock absorber (noun)
a cushion usually made of rubber or plastic that can be inflated	a mechanical damper; absorbs energy of sudden impulses
a mechanical device using confined air to absorb the shock of motion
the trapped air that supports a hovercraft a short distance above the water or ground