A loanword from German 'Sack', used in Japanese for a rucksack or backpack, often in outdoor or casual contexts. Compare with リュックサック, which is more common.
from German Sack
See also: リュックサック
I climbed the mountain trail carrying a heavy rucksack on my back.
A rucksack is essential for mountain climbing.
Before setting off, I packed food and water into my rucksack.
From German 'Sack', meaning sack or bag.