In the USA, if you say "I'm pissed" or "I'm pissed off" - it means you are angry or upset about something.
In Russian: the toilet = сортир, толчок )))))
"I'll be right back, I'm going to the loo."
This sentence means in portuguese: "Já volto, vou ao quarto de banho" .
Not so much a slang word to be honest; the Queen uses this word. Apparently saying 'loo' is better than saying 'toilet' ; it's more polite.
One American slang for toilet that I've never liked was "the John."
Military call it "the head."
I've pleasure to be member in this group
American Slang does not use "the loo"
Things like :
The potty (for kids)
The Crapper (for the man who invented it)
The porcelin God (When you are drunk, on your knees in front of it)
The lav (short for lavatory)
hello how are you