Other forms: backpacking, backpacks
A backpack is the bag you carry on your back, to school or up a mountain. Two straps, and the weight where you can carry it.
British English says rucksack for the walking kind and both words for the school kind. Hiking ones have a hip belt, which takes the load off the shoulders and makes an enormous difference. The verb gave English backpacking, meaning cheap independent travel, and a backpacker is somebody doing it. A daypack is the small version for one day out.
1nounbackpackA bag with shoulder straps carried on the back.
“She swung the backpack onto one shoulder.”
2verbtravelTo travel cheaply and independently carrying your luggage.
“They backpacked round South America for a year.”
Also accepted in games: rucksack
From back + pack. 1896.
Etymology from Wiktionary, CC BY-SA