fast food vs aliment

fast food and aliment both are nouns.

Word	Noun	Adjective	Verb	Adverb
fast food	Yes	No	No	No
aliment	Yes	No	Yes	No

As nouns, aliment is a hypernym of fast food; that is, aliment is a word with a broader meaning than fast food:

fast food: inexpensive food (hamburgers or chicken or milkshakes) prepared and served quickly
aliment: a source of materials to nourish the body

Other hypernyms of fast food include alimentation, nourishment, nutriment, nutrition, sustenance, victuals.

fast food (noun)	aliment (noun)
inexpensive food (hamburgers or chicken or milkshakes) prepared and served quickly	a source of materials to nourish the body

fast food (verb)	aliment (verb)
	give nourishment to