“Xô” is something (as I can’t quite say it’s an expression) that we say when we want something away from us, when we don’t want it to approach.
A really common and widespread one is Xô, Saravá!
Although saravá has a good connotation in a few religious groups it has received, over time, a quite bad meaning, as if it were a jinx.
That said, Xô, saravá is said to scare away jinxes of all sorts.
You can also get rid of jinxes by saying:
Mal-olhado literally means “Badly looked”, as if someone would be looking at someone or something and wishing to jinx it. But yeah, you can use it pretty much in any situation.
Você viu a cara que ela fez pra mim na minha formatura? Xô, inveja! [Go away, envy!]
Another very common use is to scare away your occasional lazyness: Xô, preguiça!
You can also say: Sai, preguiça!
I have definitely heard people scare dogs (or pretty much any animal or person) by saying that:
Xô, xô, xô! Xô, cachorro! (That almost comes out as a tongue twister)
Xô daqui! (Get outta here!)
Xô do meu lugar, Lucas.
These are expressions you’re only going to listen in real situations in a Portuguese-speaking country, not in a textbook.
You can also hear:
Rapa fora! (I particularly love this one!)
This is a poster for preventing dengue fever:
Well, this is it for today.