also: デーパック
noun
day pack
A small backpack designed for day trips or light daily use.
日帰りハイキングにはデイパックが便利だ。
A day pack is handy for a day hike.
Spelling with interpunct; mainly seen in older or stylized contexts.
Rare interpunct variant of the long-vowel spelling.
リュックサック is a general term for a backpack, while デイパック specifically refers to a smaller pack for day use.
Borrowed from English 'day pack'.