From WordNet (r) 3.0 (2006) [wn]:
backpack
n 1: a bag carried by a strap on your back or shoulder [syn:
backpack, back pack, knapsack, packsack,
rucksack, haversack]
v 1: hike with a backpack; "Every summer they are backpacking in
the Rockies" [syn: backpack, pack]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
backpack \back"pack\ n.
a bag carried on the back, supported by straps looped over
the shoulders.
Syn: knapsack; rucksack; haversack. [WordNet 1.5]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
backpack \back"pack\ v. i.
to hike while carrying a backpack; -- often used in the form
go backpacking; as, to backpack through the forest.
[PJC]