a bag with shoulder straps which allow it to be carried on someone's back, typically made of a strong, waterproof material and widely used by hikers (尤指用牢固的防水材料制成,徒步旅行者广泛使用的)帆布背包
语源
mid 19th cent.: from German, from rucken (dialect variant of Rücken 'back') + Sack 'bag, sack'