Stands for `Android Open Kang Project`, a distribution of Android ROMs based on AOSP (Android Open Source Project) and created largely by the developer roman.
AOKP stands for Android Open Kang Project. It is a custom ROM distribution for many Android devices. The name is a play on the word "kang" and AOSP (Android Open Source Project). The name was sort of a joke, but it just stuck, just like our infatuation with unicorns.
The AOKP site can be visited for more information.