From Wiktionary, the free dictionary
From piss off in the sense of annoyance.
pissoff (plural pissoffs)
- (vulgar) An annoying person, object, or event.
The biggest pissoff of my day was waiting in line for fifteen minutes only to realize I'd forgotten my coupons.
2013, Steve Wheeler, Crystal Venom[1], page 19:Can't get the arm out, guys: it's no longer responding. Disconnecting. That's a pissoff.
2018, Tom Wilson, James F. Wilson, I am Tommy: On Stage and Backstage[2], page 231:What a pissoff. Another waste of a great talent.