Well I'm glad to see clarification.

I was always told that the proper acronym was the gender-neutral POOB.

While the acronym can be used for persons of either (or these days any) sex, the meaning(s) were given to me as:

Pissed Off Old Bastard

and

Pissed Off Old Broad - or Bat - or Bitch, depending on context and usage.

With a suitably clear surrounding context, Pissed ON sometimes might seem to apply as well, although a term with too many meanings creates confusion and pisses everybody off.

John