Meaning
To be out of the loop / To be clueless
Example
Você não sabia que eles terminaram? Nossa, você está por fora!
You didn't know they broke up? Wow, you are so out of the loop!
Origin
'Por fora' literally = 'on the outside.' If you are on the outside of a group, a conversation or a development, you're unaware of it.
Practice idioms with the Idiom Trainer
Falando's Idiom Trainer teaches you to recognize idiom meanings and create sentences using them, so you can speak like a Brazilian.
More idioms
Acertar na moscaTo guess correctly / To hit the nail on the headAmigo da onçaA fake/false friendAndar na linhaTo toe the line / To behave properlyArmar um barracoTo cause a public sceneRodar a baianaTo cause a public scene / To go ballisticArrumar sarna pra se coçarTo ask for troubleArrastar as asasTo hit on someone / To flirtAbrir o jogoTo come clean / To open upArregaçar as mangasTo roll up one's sleeves / To get to workAgarrar com unhas e dentesTo hold on for dear life / To seize an opportunity