pissed off at someone/something

pissed (off) at (someone or something)

rude slang Extremely angry, disgusted, or incensed because of someone or something. Don't get pissed at me—you're the one who wanted to go through with this cockamamie scheme to begin with! A lot of people are pissed off at our government for putting the interests of companies ahead of its citizens.
See also: pissed

pissed (off) (at someone/something)

and pissed off about someone/something
mod. very angry with or about someone or something. (Objectionable to many people, but heard in all popular entertainment, schools, and the workplace.) She’s always so pissed off about something. He always seems pissed off at somebody.