Catraca Livre is a brazilian slang which means cultural, social and educational events that are free of chargeou at low-cost.
In portugueses "catraca" means turnstile, "livre" is free. So, Catraca Livre is free turnstile.
This slang was born due to a brazilian website, which informs what is possible to do without money in Sâo Paulo, Brazil´ largest city ( www.catracalivre.com.br).
It also can be translated into a open city.