A loanword from English, used for a backpack or rucksack, often in outdoor or travel contexts.
旅行にはバックパックが便利です。
A backpack is convenient for traveling.
リュックサック is the everyday Japanese word for a backpack, while バックパック is a loanword often used for larger, travel-style packs.
バックパック is a more recent loanword for backpack, often used for larger travel or hiking packs, whereas リュック is the everyday word for any backpack.
バックパック is a newer English loanword often used for travel or hiking packs, whereas ザック has a more traditional, mountaineering-club feel.
バックパック is a newer, casual loanword often used for travel backpacks, whereas ナップザック sounds slightly dated and is mostly used for simple hiking bags.
Loanword from English 'backpack'.