to dump someone, to reject someone
Ontem na festa a Camila deu um fora no Enzo, foi muito engraçado!
Yesterday at the party Camila rejected Enzo, it was really funny!
The phrase builds on the adverb fora ("out, outside"): to dar um fora in someone is to "give them the out," sending them away — hence rejecting or dumping a suitor. The same word also yields the sense of um fora as a slip or blunder, a remark that lands "outside" what was appropriate.
Falando's Idiom Trainer teaches you to recognize idiom meanings and create sentences using them, so you can speak like a Brazilian.
