General Brazilian
conversa casual / bate-papo
Both terms are commonly used; bate-papo is very popular in informal contexts
Rio de Janeiro
conversa casual / papo
Papo is a colloquial shortening frequently used
São Paulo
conversa casual / conversa descontraída
Similar to general Brazilian usage
Portugal
conversa casual / conversa descontraída
Portuguese speakers may also use 'conversa informal' or 'palestra'