knapsack vs packsack

knapsack and packsack both are nouns.

Word	Noun	Adjective	Verb	Adverb
knapsack	Yes	No	No	No
packsack	Yes	No	No	No

As nouns, knapsack and packsack are synonyms defined as:

knapsack and packsack: a bag carried by a strap on your back or shoulder

Other synonyms of knapsack include back pack, backpack, haversack, rucksack.

knapsack (noun)	packsack (noun)
a bag carried by a strap on your back or shoulder	a bag carried by a strap on your back or shoulder