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Defintion 1: to inadvertently hit someone with your backpack due to:
1. Forgetting you are wearing it.

2. Misjudging the depth a backpack adds to your frame

Defintion 2: Backwacker: a person who backwacks
Person 1: Hey, how did you get that scrape on your face?
Person 2: I was backwacked on the subway ride to work today.
by psloper November 18, 2009
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