I think is something like shoo (to surprise someone). Can someone confirm, please. 

Thank you

Its used to take someones attention like saying "hush, psst, shush, pst, sh, shoo" .

Doesnt have any meaning than this.

p.s. Pist= path, course

Yes you are right, sometimes we use it to call someone.

thank you!

Stritly speaking Pısssst! is what you say to a cat, when you want to draw his/her attention.

Not very polite to use it, addressing other humans.

I think it can be "girly" or childish more than unpolite.

Ask a youngster around you to address her class teacher as "Pıssst !"

Then ask the youngster if the teacher took it as a girly/childish act or plain lack of good manners...

Yes, you are right. But I said only the possibility.