A butt pocket is similar to an asshole. Butt pocket is an insult for someone being absent minded or ignorant. Some one being irritating or annoying would be considered a butt pocket. A butt pocket is just an insult.
Lubricant thick enough to be kept in the pockets of clothing without dripping through, often literally butter or margarine. Pocket butter is used defensively to help ease the pain, and prevent bodily damage associated with rape. Product is usually applied externally, and VERY urgently.
"I have to report tomorrow. Anything I should bring?"
"Underwear... Wear at least three white t-shirts, three pairs of drawers, and three pairs of socks. And you're a little too pretty, you may want to pack pocket butter as soon as you can."