The stuff - mostly consisting of a wallet with credit cards, some documents, random paper such as a timetable or folded advertisments - neatly stored in the back pockets. At a certain point, the mass provides a hefty bulge on the buttocks, additional protection from blows as well as possible discomfort when sitting down.
Me: Man, can't you sit still, you're squirming all the time.
Friend: Just have to lose my ass armor. *pulls out a wallet*
When your girlfriend/wife wears both panties and boxers to bed. This is used to indicate that you will not be having sex. This is often related to her being on her period. Other possible explanitions include that she is sick or unhappy with you for some reason.
When I crawled into bed my girlfriend had her ass armor on. I guess that it is that time of the month again - blowjob week!