back·pack 
(băkpăk′)
(băkpăk′)n.
1. A sturdy bag designed for carrying articles on a person's back, having shoulder straps and often mounted on a lightweight frame.
2. A piece of equipment, often containing life-support devices, designed to be used while being carried on the back: a parachute in a backpack; an astronaut's backpack.
v. back·packed, back·pack·ing, back·packs
v.intr.
To hike or travel while carrying a backpack.
v.tr.
To carry in a backpack.
backpack′er n.
backpack′ing n.