(someone) is pissed off at (someone)
Being "pissed off" means being quite angry.
I am so pissed off right now!
You get "pissed off at" a person, or "pissed off about" an idea which makes you angry:
Are you still pissed off at me about what I said this morning?
"Pissed off" is a slightly rough phrase, so avoid it in polite situations with people you don't know well.
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