1. The group of people who hang outside building doors and stairways smoking every day at work.
"TM me if the boss comes back, i be hangin with the butt posse."
2 more definitions
3. The same old group of friends who repeatedly save your ass.
"I'm giving everyone in my butt posse $5 gift cards for Christmas; think it's enuf?"
2. A bunch of guys who are banging the same chick.
"The STD clinic made her call everyone in her butt posse."