definition of barbarian

I know I repeat myself but I want to have clear one
definition.
Was "barbarian" everyone who was not greek or just a part of
them?
I think here of egyptians, known to greek, I think here of
semitic tribes, known to greek too.So could I think greeks
called the culture of egypt a "barbar" one too, when people
like Strabo and Platon worked in the bibliothek of
Alexandria?( I hope am not mistaking the dates herE:-)))
Is there a selective definition of the therm or do I have to
understand trough "barbar" everything which was not greek?