Pop Back
When you are twerking up against someone and you finish it off by dropping into the splits and twerking on their face.
"yo! she totally just pop backed me at that party last night!"
pop back
To fire a gun, typically at another person.
I pop back, you bow down...
pop at the back
southern colloq. for "fart"
Whew! Did you just pop at the back because it smells really bad in here?