at Urban dictionary result for jack bag
-Jack bag-a military issued sleeping bag that deployed soldiers sleep in and masturbate in before going to sleep at night thinking about their bitch back home or due to the absence of woman. THis sleeping bag can become very foul throughout the course of a deployment. So be weary next time you shop for a used sleeping bag at the Army surplus store.
http://www.urbandictionary.com/defin...erm=jack%20bag