meal vs foodstuff

meal and foodstuff both are nouns.

Word	Noun	Adjective	Verb	Adverb
meal	Yes	No	No	No
foodstuff	Yes	No	No	No

As nouns, foodstuff is a hypernym of meal; that is, foodstuff is a word with a broader meaning than meal:

meal: coarsely ground foodstuff; especially seeds of various cereal grasses or pulse
foodstuff: a substance that can be used or prepared for use as food

Other hypernyms of meal include food product.

meal (noun)	foodstuff (noun)
the food served and eaten at one time	(usually plural) consumer goods sold by a grocer
coarsely ground foodstuff; especially seeds of various cereal grasses or pulse	a substance that can be used or prepared for use as food
any of the occasions for eating food that occur by custom or habit at more or less fixed times