POWER BOTTOM is...

actually a bottom, yet the one in charge?

I kid you not, a 'Power Bottom' is the one calling the shots, despite being the one getting fucked.

Interesting to note that many assume that the bottom is always the submissive partner, when it comes to sex, but hey, it ain't so.

Least not all the time.

For more info visit:
Gaydemon Dicktionary.