Definition of "knapsack" in English

noun

1. (chiefly US) (in UK, dated or archaic) A case of canvas or leather, for carrying items on the back.

   • 1936, Arthur Ransome, Pigeon Post, ch 3. "All but Nancy carried knapsacks, with sandwiches and thermos flasks of tea. Peggy’s knapsack held Nancy’s provisions as well as her own, for on Nancy’s shoulders, instead of a knapsack, was a pigeon-basket […]"

2. (cryptography) A set of values from which a subset is chosen.

verb

1. To go hiking while burdened with a knapsack, usually overnight or for longer.

   • My sleeping bag fell off my backpack into the water, while we were knapsacking up the mountain.