knapsack knapsack /ˈnæpˌsæk/

noun

1. () A bag carried by a strap on your back or shoulder  ( back pack , backpack , packsack , haversack , knapsack , rucksack )
   a bag carried by a strap on your back or shoulder
    My daughter's backpack is pink and covered in unicorns
   My daughter's backpack is pink and covered in unicorns