A word often used and never defined. Look it up (or Google it).
James Joyce and Victims: Reading the Logic of Exclusion - Google Books Resultby Sean P. Murphy - 2003 - Literary Criticism - 192 pages:
... even community as flawed as the human "gossipocracy," just as he celebrates the need for community in Ulysses, where Bloom becomes a Zen-like character ...
Finnegans Wake - Page 476
by James Joyce - Fiction - 1999 - 627 pages:
... deputising for "gossipocracy," and his station was a few perch to the ...
To eliminate a hard-on (go limp) by peeing instead of ejaculation. This is disappointing to men, so they don't want to go to the bathroom and piss off their hard-on. Then then say they are pissed off, or angry about it.
It has become slang for making someone angry or when something or someone makes a person angry.
Today, women have picked up on this term also, using it as getting angry (but not about their hard-on going away).
I love my errection, but when I go pee it will piss off (original usage).
He is going to piss me off (modern).